Life science

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field of science, such as biology, that studies living things.

Glossary of life sciences

  • macroevolution - noun evolution on a large scale extending over geologic era and resulting in the formation of new taxonomic groups
  • microevolution - noun evolution resulting from small specific genetic changes that can lead to a new subspecies
  • helix - noun type genus of the family Helicidae; a curve that lies on the surface of a cylinder or cone and cuts the element at a constant angle; a structure consisting of something wound in a continuous series of loops
  • degenerate - adj. unrestrained by convention or morality; noun a person whose behavior deviates from what is acceptable especially in sexual behavior; verb grow worse
  • A-horizon - noun the top layer of a soil profile; usually contains humus
  • abdomen - noun the region of the body of a vertebrate between the thorax and the pelvis; the cavity containing the major viscera; in mammals it is separated from the thorax by the diaphragm
  • Abduction - noun (physiology) moving of a body part away from the central axis of the body; the criminal act of capturing and carrying away by force a family member; if a man's wife is abducted it is a crime against the family relationship and against the wife
  • abduction - noun (physiology) moving of a body part away from the central axis of the body; the criminal act of capturing and carrying away by force a family member; if a man's wife is abducted it is a crime against the family relationship and against the wife
  • ABA - noun a fabric woven from goat hair and camel hair; a loose sleeveless outer garment made from aba cloth; worn by Arabs
  • abscission - noun the act of cutting something off; shedding of flowers and leaves and fruit following formation of scar tissue in a plant
  • absorption spectrum - noun the spectrum of electromagnetic radiation that has passed through a medium that absorbed radiation of certain wavelengths
  • abstract - adj. existing only in the mind; separated from embodiment; dealing with a subject in the abstract without practical purpose or intention; not representing or imitating external reality or the objects of nature; noun a concept or idea not associated with any specific instance; a sketchy summary of the main points of an argument or theory; verb consider a concept without thinking of a specific example; consider abstractly or theoretically; consider apart from a particular case or instance; give an abstract (of); make off with belongings of others
  • abyssal zone - noun the deep sea (2000 meters or more) where there is no light
  • accessory fruit - noun fruit containing much fleshy tissue besides that of the ripened ovary; as apple or strawberry
  • acclimatization - noun adaptation to a new climate (a new temperature or altitude or environment)
  • acellular - adj. not made up of or divided into cells
  • acetylcholine - noun a neurotransmitter that is a derivative of choline; released at the ends of nerve fibers in the somatic and parasympathetic nervous systems
  • acid - adj. having the characteristics of an acid; harsh or corrosive in tone; being sour to the taste; noun street name for lysergic acid diethylamide; any of various water-soluble compounds having a sour taste and capable of turning litmus red and reacting with a base to form a salt
  • Acid rain - noun rain containing acids that form in the atmosphere when industrial gas emissions (especially sulfur dioxide and nitrogen oxides) combine with water
  • acid rain - noun rain containing acids that form in the atmosphere when industrial gas emissions (especially sulfur dioxide and nitrogen oxides) combine with water
  • acidophile - noun an organism that thrives in a relatively acid environment
  • acromegaly - noun enlargement of bones of hands and feet and face; often accompanied by headache and muscle pain and emotional disturbances; caused by overproduction of growth hormone by the anterior pituitary gland (due to a tumor)
  • Actin - noun one of the proteins into which actomyosin can be split; can exist in either a globular or a fibrous form
  • actin - noun one of the proteins into which actomyosin can be split; can exist in either a globular or a fibrous form
  • action potential - noun the local voltage change across the cell wall as a nerve impulse is transmitted
  • activation energy - noun the energy that an atomic system must acquire before a process (such as an emission or reaction) can occur
  • activator - noun (biology) any agency bringing about activation; a molecule that increases the activity of an enzyme or a protein that increases the production of a gene product in DNA transcription
  • active site - noun the part of an enzyme or antibody where the chemical reaction occurs
  • Active transport - noun transport of a substance (as a protein or drug) across a cell membrane against the concentration gradient; requires an expenditure of energy
  • active transport - noun transport of a substance (as a protein or drug) across a cell membrane against the concentration gradient; requires an expenditure of energy
  • adaptation - noun (physiology) the responsive adjustment of a sense organ (as the eye) to varying conditions (as of light); a written work (as a novel) that has been recast in a new form; the process of adapting to something (such as environmental conditions)
  • adaptive radiation - noun the development of many different forms from an originally homogeneous group of organisms as they fill different ecological niches
  • Adduction - noun (physiology) moving of a body part toward the central axis of the body
  • adduction - noun (physiology) moving of a body part toward the central axis of the body
  • adenosine triphosphate - noun a nucleotide derived from adenosine that occurs in muscle tissue; the major source of energy for cellular reactions
  • adhesion - noun a fibrous band of scar tissue that binds together normally separate anatomical structures; abnormal union of bodily tissues; most common in the abdomen; faithful support for a religion or cause or political party; the property of sticking together (as of glue and wood) or the joining of surfaces of different composition
  • adrenal cortex - noun the cortex of the adrenal gland; secretes corticosterone and sex hormones
  • adrenal gland - noun either of a pair of complex endocrine glands situated near the kidney
  • adrenal medulla - noun the medulla of the adrenal gland; secretes epinephrine
  • ACTH - noun a hormone produced by the anterior pituitary gland that stimulates the adrenal cortex
  • Adventitious - adj. associated by chance and not an integral part
  • adventitious - adj. associated by chance and not an integral part
  • aerobic - adj. depending on free oxygen or air; based on or using the principles of aerobics; enhancing respiratory and circulatory efficiency
  • affinity - noun a natural attraction or feeling of kinship; inherent resemblance between persons or things; the force attracting atoms to each other and binding them together in a molecule;(immunology) the attraction between an antigen and an antibody; a close connection marked by community of interests or similarity in nature or character; (biology) state of relationship between organisms or groups of organisms resulting in resemblance in structure or structural parts; (anthropology) kinship by marriage or adoption; not a blood relationship
  • aggregate fruit - noun fruit consisting of many individual small fruits or drupes derived from separate ovaries within a common receptacle: e.g. blackberry; raspberry; pineapple
  • Agnatha - noun superclass of eel-shaped chordates lacking jaws and pelvic fins: lampreys; hagfishes; some extinct forms
  • aldosterone - noun a corticosteroid hormone that is secreted by the cortex of the adrenal gland; regulates salt (sodium and potassium) and water balance
  • aleurone - noun granular protein in outermost layer of endosperm of many seeds or cereal grains
  • alimentary canal - noun tubular passage of mucous membrane and muscle extending about 8.3 meters from mouth to anus; functions in digestion and elimination
  • allantois - noun vascular fetal membrane that develops from the hindgut in embryonic higher vertebrates (reptiles, birds and mammals)
  • allele - noun either of a pair (or series) of alternative forms of a gene that can occupy the same locus on a particular chromosome and that control the same character
  • allergy - noun hypersensitivity reaction to a particular allergen; symptoms can vary greatly in intensity
  • helix - noun type genus of the family Helicidae; a curve that lies on the surface of a cylinder or cone and cuts the element at a constant angle; a structure consisting of something wound in a continuous series of loops
  • alteration - noun the act of making something different (as e.g. the size of a garment); the act of revising or altering (involving reconsideration and modification); an event that occurs when something passes from one state or phase to another
  • alveolus - noun a tiny sac for holding air in the lungs; formed by the terminal dilation of tiny air passageways; a bony socket in the alveolar ridge that holds a tooth
  • ambulacral - adj. pertaining to the ambulacra of radial echinoderms
  • system - noun instrumentality that combines interrelated interacting artifacts designed to work as a coherent entity; the living body considered as made up of interdependent components forming a unified whole; a group of physiologically or anatomically related organs or parts; a complex of methods or rules governing behavior;a procedure or process for obtaining an objective; a group of independent but interrelated elements comprising a unified whole;(physical chemistry) a sample of matter in which substances in different phases are in equilibrium; an ordered manner; orderliness by virtue of being methodical and well organized; an organized structure for arranging or classifying
  • amino acid - noun organic compounds containing an amino group and a carboxylic acid group
  • ammonia - noun a pungent gas compounded of nitrogen and hydrogen (NH3); a water solution of ammonia
  • ammonification - noun impregnation with ammonia or a compound of ammonia
  • amnion - noun thin innermost membranous sac enclosing the developing embryo of higher vertebrates (reptiles, birds and mammals)
  • amniote - noun any member of the Amniota
  • Amphibia - noun the class of vertebrates that live on land but breed in water; frogs; toads; newts; salamanders; caecilians
  • amygdala - noun an almond-shaped neural structure in the anterior part of the temporal lobe of the cerebrum; intimately connected with the hypothalamus and the hippocampus and the cingulate gyrus; as part of the limbic system it plays an important role in motivation and emotional behavior
  • Anabolic - adj. characterized by or promoting constructive metabolism; of or related to the synthetic phase of metabolism
  • anabolic - adj. characterized by or promoting constructive metabolism; of or related to the synthetic phase of metabolism
  • anaerobic - adj. living or active in the absence of free oxygen; not aerobic
  • Anaphase - noun the stage of meiosis or mitosis when chromosomes move toward opposite ends of the nuclear spindle
  • anaphase - noun the stage of meiosis or mitosis when chromosomes move toward opposite ends of the nuclear spindle
  • anapsid - noun primitive reptile having no opening in the temporal region of the skull; all extinct except turtles
  • androgen - noun male sex hormone that is produced in the testes and responsible for typical male sexual characteristics
  • aneuploid - adj. having a chromosome number that is not an exact multiple of the haploid number
  • aneuploidy - noun an abnormality involving a chromosome number that is not an exact multiple of the haploid number (one chromosome set is incomplete)
  • angina - noun any disease of the throat or fauces marked by spasmodic attacks of intense suffocative pain; a heart condition marked by paroxysms of chest pain due to reduced oxygen to the heart
  • ACE - adj. of the highest quality; noun a serve that the receiver is unable to reach; one of four playing cards in a deck having a single pip on its face; someone who is dazzlingly skilled in any field; a major strategic headquarters of NATO; safeguards an area extending from Norway to Turkey; verb serve an ace against (someone); play (a hole) in one stroke; score an ace against;succeed at easily
  • ACE - adj. of the highest quality; noun a serve that the receiver is unable to reach; one of four playing cards in a deck having a single pip on its face; someone who is dazzlingly skilled in any field; a major strategic headquarters of NATO; safeguards an area extending from Norway to Turkey; verb serve an ace against (someone); play (a hole) in one stroke; score an ace against;succeed at easily
  • angiotensin I - noun a physiologically inactive form of angiotensin that is the precursor to angiotensin II
  • angiotensin II - noun a potent vasopressor agent formed from angiotensin I
  • anion - noun a negatively charged ion
  • Annelida - noun segmented worms: earthworms; lugworms; leeches
  • anoxic - adj. relating to or marked by a severe deficiency of oxygen in tissues or organs
  • anterior pituitary - noun the anterior lobe of the pituitary body; primarily glandular in nature
  • anther - noun the part of the stamen that contains pollen; usually borne on a stalk
  • antheridium - noun the male sex organ of spore-producing plants; produces antherozoids; equivalent to the anther in flowers
  • Anthophyta - noun comprising flowering plants that produce seeds enclosed in an ovary; in some systems considered a class (Angiospermae) and in others a division (Magnoliophyta or Anthophyta)
  • anthropoid - adj. resembling human beings; resembling apes; nounany member of the suborder Anthropoidea including monkeys and apes and hominids; person who resembles a nonhuman primate
  • ADH - noun hormone secreted by the posterior pituitary gland (trade name Pitressin) and also by nerve endings in the hypothalamus; affects blood pressure by stimulating capillary muscles and reduces urine flow by affecting reabsorption of water by kidney tubules
  • antibiotic - adj. of or relating to antibiotic drugs; noun a chemical substance derivable from a mold or bacterium that kills microorganisms and cures infections
  • antibody - noun any of a large variety of proteins normally present in the body or produced in response to an antigen which it neutralizes, thus producing an immune response
  • antidiuretic hormone - noun hormone secreted by the posterior pituitary gland (trade name Pitressin) and also by nerve endings in the hypothalamus; affects blood pressure by stimulating capillary muscles and reduces urine flow by affecting reabsorption of water by kidney tubules
  • ADH - noun hormone secreted by the posterior pituitary gland (trade name Pitressin) and also by nerve endings in the hypothalamus; affects blood pressure by stimulating capillary muscles and reduces urine flow by affecting reabsorption of water by kidney tubules
  • antigen - noun any substance (as a toxin or enzyme) that stimulates an immune response in the body (especially the production of antibodies)
  • APC - noun a drug combination found in some over-the-counter headache remedies (aspirin and phenacetin and caffeine); (military) an armored vehicle (usually equipped with treads) that is used to transport infantry
  • antioxidant - noun substance that inhibits oxidation or inhibits reactions promoted by oxygen or peroxides
  • antipodal - adj. relating to the antipodes or situated at opposite sides of the earth; noun the relation of opposition along a diameter
  • Anura - noun frogs, toads, tree toads
  • anus - noun excretory opening at the end of the alimentary canal
  • aorta - noun the large trunk artery that carries blood from the left ventricle of the heart to branch arteries
  • apocrine gland - noun a large sweat gland that produces both a fluid and an apocrine secretion; in human beings located in hairy regions of the body
  • apodeme - noun ridge-like ingrowth of the exoskeleton of an arthropod that supports internal organs and provides attachment points for muscles
  • apomixis - noun any of several kinds of reproduction without fertilization
  • apoptosis - noun a type of cell death in which the cell uses specialized cellular machinery to kill itself; a cell suicide mechanism that enables metazoans to control cell number and eliminate cells that threaten the animal's survival
  • aposematic coloration - noun conspicuous coloration or markings of an animal serving to warn off predators
  • appendicular skeleton - noun the part of the skeleton that includes the pectoral girdle and the pelvic girdle and the upper and lower limbs
  • applied science - noun the discipline dealing with the art or science of applying scientific knowledge to practical problems
  • Archaeopteryx - noun extinct primitive toothed bird of the Jurassic period having a long feathered tail and hollow bones; usually considered the most primitive of all birds
  • archegonium - noun a female sex organ occurring in mosses, ferns, and most gymnosperms
  • archenteron - noun central cavity of the gastrula; becomes the intestinal or digestive cavity
  • archosaur - noun extinct reptiles including: dinosaurs; plesiosaurs; pterosaurs; ichthyosaurs; thecodonts
  • aromatic hydrocarbon - noun a hydrocarbon that contains one or more benzene rings that are characteristic of the benzene series of organic compounds
  • arteriole - noun one of the small thin-walled arteries that end in capillaries
  • artery - noun a major thoroughfare that bears important traffic; a blood vessel that carries blood from the heart to the body
  • Arthropoda - noun jointed-foot invertebrates: arachnids; crustaceans; insects; millipedes; centipedes
  • articulation - noun the act of joining things in such a way that motion is possible; expressing in coherent verbal form; the aspect of pronunciation that involves bringing articulatory organs together so as to shape the sounds of speech; the shape or manner in which things come together and a connection is made; (anatomy) the point of connection between two bones or elements of a skeleton (especially if it allows motion)
  • ascocarp - noun mature fruiting body of an ascomycetous fungus
  • Ascomycota - noun a large subdivision of Eumycota including Hemiascomycetes and Plectomycetes and Pyrenomycetes and Discomycetes; sac fungi; in some classification systems considered a division of the kingdom Fungi
  • ascus - noun saclike structure in which ascospores are formed through sexual reproduction of ascomycetes
  • Assimilation - noun in the theories of Jean Piaget: the application of a general schema to a particular instance; a linguistic process by which a sound becomes similar to an adjacent sound; the process of absorbing nutrients into the body after digestion; the social process of absorbing one cultural group into harmony with another; the state of being assimilated; people of different backgrounds come to see themselves as part of a larger national family; the process of assimilating new ideas into an existing cognitive structure
  • assimilation - noun in the theories of Jean Piaget: the application of a general schema to a particular instance; a linguistic process by which a sound becomes similar to an adjacent sound; the process of absorbing nutrients into the body after digestion; the social process of absorbing one cultural group into harmony with another; the state of being assimilated; people of different backgrounds come to see themselves as part of a larger national family; the process of assimilating new ideas into an existing cognitive structure
  • assortative mating - noun mating of individuals having more traits in common than likely in random mating
  • astrocyte - noun comparatively large neuroglial cell
  • Asymmetrical - adj. irregular in shape or outline; characterized by asymmetry in the spatial arrangement or placement of parts or components
  • asymmetrical - adj. irregular in shape or outline; characterized by asymmetry in the spatial arrangement or placement of parts or components
  • Atherosclerosis - noun a stage of arteriosclerosis involving fatty deposits (atheromas) inside the arterial walls
  • atherosclerosis - noun a stage of arteriosclerosis involving fatty deposits (atheromas) inside the arterial walls
  • atom - noun (nontechnical usage) a tiny piece of anything; (physics and chemistry) the smallest component of an element having the chemical properties of the element
  • atomic mass - noun (chemistry) the mass (in atomic mass units) of an isotope of an element
  • atomic number - noun the order of an element in Mendeleyev's table of the elements; equal to the number of protons in the nucleus or electrons in the neutral state of an atom of an element
  • ATP - noun a nucleotide derived from adenosine that occurs in muscle tissue; the major source of energy for cellular reactions
  • atrioventricular valve - noun either of two heart valves through which blood flows from the atria to the ventricles; prevents return of blood to the atrium
  • atrium - noun the central area in a building; open to the sky; any chamber that is connected to other chambers or passageways (especially one of the two upper chambers of the heart)
  • hyperactivity - noun a condition characterized by excessive restlessness and movement
  • disorder - noun a disturbance of the peace or of public order;condition in which there is a disturbance of normal functioning; a condition in which things are not in their expected places; verb bring disorder to; disturb in mind or make uneasy or cause to be worried or alarmed
  • ADHD - noun a condition (mostly in boys) characterized by behavioral and learning disorders
  • attenuation - noun the property of something that has been weakened or reduced in thickness or density; weakening in force or intensity
  • Audition - noun a test of the suitability of a performer; the ability to hear; the auditory faculty; verb perform in order to get a role
  • audition - noun a test of the suitability of a performer; the ability to hear; the auditory faculty; verb perform in order to get a role
  • auditory ossicle - noun ossicles of the middle ear that transmit acoustic vibrations from the eardrum to the inner ear
  • autoantibody - noun an antibody acting against tissues of the organism that produces it
  • Autoimmunity - noun production of antibodies against the tissues of your own body; produces autoimmune disease or hypersensitivity reactions
  • autoimmunity - noun production of antibodies against the tissues of your own body; produces autoimmune disease or hypersensitivity reactions
  • autonomic nervous system - noun the part of the nervous system of vertebrates that controls involuntary actions of the smooth muscles and heart and glands
  • autosome - noun any chromosome that is not a sex chromosome; appear in pairs in body cells but as single chromosomes in spermatozoa
  • auxin - noun a plant hormone that promotes root formation and bud growth
  • avidity - noun a positive feeling of wanting to push ahead with something
  • axial skeleton - noun the part of the skeleton that includes the skull and spinal column and sternum and ribs
  • axon - noun long nerve fiber that conducts away from the cell body of the neuron
  • AZT - noun an antiviral drug (trade name Retrovir) used in the treatment of AIDS; adverse side effects include liver damage and suppression of the bone marrow
  • B - noun the blood group whose red cells carry the B antigen; the 2nd letter of the Roman alphabet; aerobic rod-shaped spore-producing bacterium; often occurring in chainlike formations; found primarily in soil; (physics) a unit of nuclear cross section; the effective circular area that one particle presents to another as a target for an encounter; a logarithmic unit of sound intensity equal to 10 decibels; a trivalent metalloid element; occurs both in a hard black crystal and in the form of a yellow or brown powder; originally thought to be a single vitamin but now separated into several B vitamins
  • B cell - noun a lymphocyte derived from bone marrow that provides humoral immunity; it recognizes free antigen molecules in solution and matures into plasma cells that secrete immunoglobulin (antibodies) that inactivate the antigens
  • B-horizon - noun immediately below the A-horizon; contains deposits of organic matter leached from surface soils
  • bark - noun a sailing ship with 3 (or more) masts; the sound made by a dog; a noise resembling the bark of a dog; tough protective covering of the woody stems and roots of trees and other woody plants; verb tan (a skin) with bark tannins; speak in an unfriendly tone; make barking sounds; remove the bark of a tree; cover with bark
  • BMR - noun the rate at which heat is produced by an individual in a resting state
  • base - adj. debased; not genuine; illegitimate; having or showing an ignoble lack of honor or morality; of low birth or station (`base' is archaic in this sense); not adhering to ethical or moral principles;(used of metals) consisting of or alloyed with inferior metal; serving as or forming a base; noun a support or foundation; place that runner must touch before scoring; (electronics) the part of a transistor that separates the emitter from the collector; installation from which a military force initiates operations; a flat bottom on which something is intended to sit; the principal ingredient of a mixture; the place where you are stationed and from which missions start and end; (anatomy) the part of an organ nearest its point of attachment; the bottom or lowest part; (numeration system) the positive integer that is equivalent to one in the next higher counting place; the bottom side of a geometric figure from which the altitude can be constructed; any of various water-soluble compounds capable of turning litmus blue and reacting with an acid to form a salt and water; lowest support of a structure; the stock of basic facilities and capital equipment needed for the functioning of a country or area; the fundamental assumptions from which something is begun or developed or calculated or explained; (linguistics) the form of a word after all affixes are removed; a lower limit; a terrorist network intensely opposed to the United States that dispenses money and logistical support and training to a wide variety of radical Islamic terrorist groups; has cells in more than 50 countries; the most important or necessary part of something; verb use as a basis for; found on; assign to a station; use (purified cocaine) by burning it and inhaling the fumes
  • basidiocarp - noun the fruiting body of a basidiomycete which bears its spores on special cells
  • Basidiomycota - noun comprises fungi bearing the spores on a basidium; includes Gasteromycetes (puffballs) and Tiliomycetes comprising the orders Ustilaginales (smuts) and Uredinales (rusts) and Hymenomycetes (mushrooms, toadstools, agarics and bracket fungi); in some classification systems considered a division of kingdom Fungi
  • basidium - noun a small club-shaped structure typically bearing four basidiospores at the ends of minute projections; unique to basidiomycetes
  • basilar membrane - noun a membrane in the cochlea that supports the organ of Corti
  • basophil - noun a leukocyte with basophilic granules easily stained by basic stains
  • bedrock - noun solid unweathered rock lying beneath surface deposits of soil; principles from which other truths can be derived
  • Behavior - noun manner of acting or controlling yourself;(psychology) the aggregate of the responses or reactions or movements made by an organism in any situation; the action or reaction of something (as a machine or substance) under specified circumstances; (behavioral attributes) the way a person behaves toward other people
  • behavior - noun manner of acting or controlling yourself;(psychology) the aggregate of the responses or reactions or movements made by an organism in any situation; the action or reaction of something (as a machine or substance) under specified circumstances; (behavioral attributes) the way a person behaves toward other people
  • beta cell - noun a cell that produces insulin in the isles of Langerhans in the pancreas
  • bicarbonate - noun a salt of carbonic acid (containing the anion HCO3) in which one hydrogen atom has been replaced; an acid carbonate
  • ion - noun a particle that is electrically charged (positive or negative); an atom or molecule or group that has lost or gained one or more electrons
  • bicuspid valve - noun valve with two cusps; situated between the left atrium and the left ventricle
  • Bile - noun a digestive juice secreted by the liver and stored in the gallbladder; aids in the digestion of fats
  • bile - noun a digestive juice secreted by the liver and stored in the gallbladder; aids in the digestion of fats
  • binary - adj. consisting of two (units or components or elements or terms) or based on two; of or pertaining to a number system have 2 as its base; noun a system of two stars that revolve around each other under their mutual gravitation
  • prokaryotic - adj. having cells that lack membrane-bound nuclei
  • fission - noun a nuclear reaction in which a massive nucleus splits into smaller nuclei with the simultaneous release of energy;reproduction of some unicellular organisms by division of the cell into two more or less equal parts
  • biochemistry - noun the organic chemistry of compounds and processes occuring in organisms; the effort to understand biology within the context of chemistry
  • biodiversity - noun the diversity of plant and animal life in a particular habitat (or in the world as a whole)
  • Biogeography - noun dealing with the geographical distribution of animals and plants
  • biogeography - noun dealing with the geographical distribution of animals and plants
  • biology - noun the science that studies living organisms;characteristic life processes and phenomena of living organisms; all the plant and animal life of a particular region
  • bioluminescence - noun luminescence produced by physiological processes (as in the firefly)
  • Biomass - noun the total mass of living matter in a given unit area;plant materials and animal waste used as fuel
  • biomass - noun the total mass of living matter in a given unit area;plant materials and animal waste used as fuel
  • biome - noun a major biotic community characterized by the dominant forms of plant life and the prevailing climate
  • bioremediation - noun the act of treating waste or pollutants by the use of microorganisms (as bacteria) that can break down the undesirable substances; the branch of biotechnology that uses biological process to overcome environmental problems
  • biosphere - noun the regions of the surface and atmosphere of the Earth (or other planet) where living organisms exist
  • Biotechnology - noun the branch of engineering science in which biological science is used to study the relation between workers and their environments; the branch of molecular biology that studies the use of microorganisms to perform specific industrial processes
  • biotechnology - noun the branch of engineering science in which biological science is used to study the relation between workers and their environments; the branch of molecular biology that studies the use of microorganisms to perform specific industrial processes
  • biotic - adj. of or relating to living organisms
  • biramous - adj. resembling a fork; divided or separated into two branches
  • birth rate - noun the ratio of live births in an area to the population of that area; expressed per 1000 population per year
  • B - noun the blood group whose red cells carry the B antigen; the 2nd letter of the Roman alphabet; aerobic rod-shaped spore-producing bacterium; often occurring in chainlike formations; found primarily in soil; (physics) a unit of nuclear cross section; the effective circular area that one particle presents to another as a target for an encounter; a logarithmic unit of sound intensity equal to 10 decibels; a trivalent metalloid element; occurs both in a hard black crystal and in the form of a yellow or brown powder; originally thought to be a single vitamin but now separated into several B vitamins
  • Black Death - noun the epidemic form of bubonic plague experienced during the Middle Ages when it killed nearly half the people of western Europe
  • blastopore - noun the opening into the archenteron
  • blastula - noun early stage of an embryo produced by cleavage of an ovum; a liquid-filled sphere whose wall is composed of a single layer of cells; during this stage (about eight days after fertilization) implantation in the wall of the uterus occurs
  • Blood pressure - noun the pressure of the circulating blood against the walls of the blood vessels; results from the systole of the left ventricle of the heart; sometimes measured for a quick evaluation of a person's health
  • blood pressure - noun the pressure of the circulating blood against the walls of the blood vessels; results from the systole of the left ventricle of the heart; sometimes measured for a quick evaluation of a person's health
  • BUN - noun small rounded bread either plain or sweet
  • bolus - noun a large pill; used especially in veterinary medicine; a small round soft mass (as of chewed food)
  • Bone - adj. consisting of or made up of bone; noun a shade of white the color of bleached bones; rigid connective tissue that makes up the skeleton of vertebrates; the porous calcified substance from which bones are made; verb remove the bones from; study intensively, as before an exam
  • bone - adj. consisting of or made up of bone; noun a shade of white the color of bleached bones; rigid connective tissue that makes up the skeleton of vertebrates; the porous calcified substance from which bones are made; verb remove the bones from; study intensively, as before an exam
  • botany - noun the branch of biology that studies plants; all the plant life in a particular region or period
  • botulism - noun food poisoning from ingesting botulin; not infectious; affects the CNS; can be fatal if not treated promptly
  • Bowman's capsule - noun thin double membrane surrounding the glomerulus of a nephron
  • brachiation - noun swinging by the arms from branch to branch
  • brainstem - noun the part of the brain continuous with the spinal cord and comprising the medulla oblongata and pons and midbrain and parts of the hypothalamus
  • bronchiole - noun any of the smallest bronchial ducts; ending in alveoli
  • bronchus - noun either of the two main branches of the trachea
  • budding - adj. beginning to develop; noun reproduction of some unicellular organisms (such as yeasts) by growth and specialization followed by the separation by constriction of a part of the parent
  • Budding - adj. beginning to develop; noun reproduction of some unicellular organisms (such as yeasts) by growth and specialization followed by the separation by constriction of a part of the parent
  • buffer - noun a cushion-like device that reduces shock due to contact; a power tool used to buff surfaces; (computer science) a part of RAM used for temporary storage of data that is waiting to be sent to a device; used to compensate for differences in the rate of flow of data between components of a computer system; an ionic compound that resists changes in its pH; an implement consisting of soft material mounted on a block; used for polishing (as in manicuring); an inclined metal frame at the front of a locomotive to clear the track; verb add a buffer (a solution); protect from impact
  • bulb - noun a rounded part of a cylindrical instrument (usually at one end); a rounded dilation or expansion in a canal or vessel or organ;a modified bud consisting of a thickened globular underground stem serving as a reproductive structure; electric lamp consisting of a transparent or translucent glass housing containing a wire filament (usually tungsten) that emits light when heated by electricity; lower or hindmost part of the brain; continuous with spinal cord; (`bulb' is an old term for medulla oblongata)
  • bulbourethral gland - noun either of two glands that discharge a component of seminal fluid into the urethra; homologous to Bartholin's gland in the female
  • B-horizon - noun immediately below the A-horizon; contains deposits of organic matter leached from surface soils
  • C - noun the 3rd letter of the Roman alphabet; (music) the keynote of the scale of C major; a general-purpose programing language closely associated with the UNIX operating system; street names for cocaine; a unit of electrical charge equal to the amount of charge transferred by a current of 1 ampere in 1 second; a degree on the centigrade scale of temperature; an abundant nonmetallic tetravalent element occurring in three allotropic forms: amorphous carbon and graphite and diamond; occurs in all organic compounds;a base found in DNA and RNA and derived from pyrimidine; pairs with guanine; one of the four nucleotides used in building DNA; all four nucleotides have a common phosphate group and a sugar (ribose); the speed at which light travels in a vacuum; the constancy and universality of the speed of light is recognized by defining it to be exactly 299,792,458 meters per second
  • C-horizon - noun beneath the B-horizon and above the bedrock; consisting of weathered rock
  • caecilian - adj. of or relating to or belonging to the family Caeciliidae; noun any of the small slender limbless burrowing wormlike amphibians of the order Gymnophiona; inhabit moist soil in tropical regions
  • Calcification - noun a process that impregnates something with calcium (or calcium salts); an inflexible and unchanging state; tissue hardened by deposition of lime salts
  • calcification - noun a process that impregnates something with calcium (or calcium salts); an inflexible and unchanging state; tissue hardened by deposition of lime salts
  • calcitonin - noun thyroid hormone that tends to lower the level of calcium in the blood plasma and inhibit resorption of bone
  • calorie - noun unit of heat defined as the quantity of heat required to raise the temperature of 1 gram of water by 1 degree centigrade at atmospheric pressure; a unit of heat equal to the amount of heat required to raise the temperature of one kilogram of water by one degree at one atmosphere pressure; used by nutritionists to characterize the energy-producing potential in food
  • calyx - noun (botany) the whorl of sepals of a flower collectively forming the outer floral envelope or layer of the perianth enclosing and supporting the developing bud; usually green
  • camouflage - noun device or stratagem for concealment or deceit;fabric dyed with splotches of green and brown and black and tan; intended to make the wearer of a garment made of this fabric hard to distinguish from the background; the act of concealing the identity of something by modifying its appearance; an outward semblance that misrepresents the true nature of something; verb disguise by camouflaging; exploit the natural surroundings to disguise something
  • canaliculus - noun a small canal or duct as in some bones and parts of plants
  • candela - noun the basic unit of luminous intensity adopted under the Systeme International d'Unites; equal to 1/60 of the luminous intensity per square centimeter of a black body radiating at the temperature of 2,046 degrees Kelvin
  • canopy - noun a covering (usually of cloth) that serves as a roof to shelter an area from the weather; the umbrellalike part of a parachute that fills with air; the transparent covering of an aircraft cockpit; verb cover with a canopy
  • capillary - adj. long and slender with a very small internal diameter;of or relating to hair; noun a tube of small internal diameter; holds liquid by capillary action; any of the minute blood vessels connecting arterioles with venules
  • capillary action - noun a phenomenon associated with surface tension and resulting in the elevation or depression of liquids in capillaries
  • capillary bed - noun a layer of tissue densely packed with capillaries
  • capsid - noun the outer covering of protein surrounding the nucleic acid of a virus; a variety of leaf bug
  • capsule - noun a pill in the form of a small rounded gelatinous container with medicine inside; a small container; a structure that encloses a body part; a dry dehiscent seed vessel or the spore-containing structure of e.g. mosses; a pilot's seat in an airplane that can be forcibly ejected in the case of an emergency; then the pilot descends by parachute; a spacecraft designed to transport people and support human life in outer space; a shortened version of a written work; verb enclose in a capsule; put in a short or concise form; reduce in volume
  • carapace - noun hard outer covering or case of certain organisms such as arthropods and turtles
  • carbohydrate - noun an essential structural component of living cells and source of energy for animals; includes simple sugars with small molecules as well as macromolecular substances; are classified according to the number of monosaccharide groups they contain
  • carbon - noun a copy made with carbon paper; an abundant nonmetallic tetravalent element occurring in three allotropic forms: amorphous carbon and graphite and diamond; occurs in all organic compounds; a thin paper coated on one side with a dark waxy substance (often containing carbon); used to transfer characters from the original to an under sheet of paper
  • CA - noun a state in the western United States on the Pacific; the 3rd largest state; known for earthquakes; a white metallic element that burns with a brilliant light; the fifth most abundant element in the earth's crust; an important component of most plants and animals
  • CA - noun a state in the western United States on the Pacific; the 3rd largest state; known for earthquakes; a white metallic element that burns with a brilliant light; the fifth most abundant element in the earth's crust; an important component of most plants and animals
  • cardiac cycle - noun the complete cycle of events in the heart from the beginning of one heart beat to the beginning of the next; an electrical impulse conducted through the heart muscle that constricts the atria which is followed by constriction of the ventricles
  • cardiac output - noun the amount of blood pumped out by the ventricles in a given period of time
  • carnivore - noun any animal that feeds on flesh; a terrestrial or aquatic flesh-eating mammal
  • carotenoid - noun any of a class of highly unsaturated yellow to red pigments occurring in plants and animals
  • carpel - noun a simple pistil or one element of a compound pistil
  • carpus - noun a joint between the distal end of the radius and the proximal row of carpal bones
  • K - noun street names for ketamine; the 11th letter of the Roman alphabet; a unit of information equal to one thousand (1024) bytes;the basic unit of thermodynamic temperature adopted under the Systeme International d'Unites; a light soft silver-white metallic element of the alkali metal group; oxidizes rapidly in air and reacts violently with water; is abundant in nature in combined forms occurring in sea water and in carnallite and kainite and sylvite
  • Cartilage - noun tough elastic tissue; mostly converted to bone in adults
  • cartilage - noun tough elastic tissue; mostly converted to bone in adults
  • catabolic - adj. characterized by destructive metabolism; relating to or characterized by catabolism
  • CAP - noun a tight-fitting headdress; a top (as for a bottle);something serving as a cover or protection; a fruiting structure resembling an umbrella that forms the top of a stalked fleshy fungus such as a mushroom; the upper part of a column that supports the entablature; dental appliance consisting of an artificial crown for a tooth; a mechanical or electrical explosive device or a small amount of explosive; can be used to initiate the reaction of a disrupting explosive; an upper limit on what is allowed; verb restrict the number or amount of; lie at the top of
  • cation - noun a positively charged ion
  • cell - noun (biology) the basic structural and functional unit of all organisms; they may exist as independent units of life (as in monads) or may form colonies or tissues as in higher plants and animals; a device that delivers an electric current as the result of a chemical reaction; a room where a prisoner is kept; small room is which a monk or nun lives; any small compartment; a small unit serving as part of or as the nucleus of a larger political movement; a hand-held mobile radiotelephone for use in an area divided into small sections, each with its own short-range transmitter/receiver
  • cell theory - noun (biology) the theory that cells form the fundamental structural and functional units of all living organisms; proposed in 1838 by Matthias Schleiden and by Theodor Schwann
  • cell wall - noun a rigid layer of polysaccharides enclosing the membrane of plant and prokaryotic cells; maintains the shape of the cell and serves as a protective barrier
  • response - noun a phrase recited or sung by the congregation following a versicle by the priest or minister; a result; a bodily process occurring due to the effect of some foregoing stimulus or agent; the manner in which something is greeted; a statement (either spoken or written) that is made in reply to a question or request or criticism or accusation; the speech act of continuing a conversational exchange
  • Cellulose - noun a polysaccharide that is the chief constituent of all plant tissues and fibers
  • cellulose - noun a polysaccharide that is the chief constituent of all plant tissues and fibers
  • cM - noun a metric unit of length equal to one hundredth of a meter;a radioactive transuranic metallic element; produced by bombarding plutonium with helium nuclei
  • cM - noun a metric unit of length equal to one hundredth of a meter;a radioactive transuranic metallic element; produced by bombarding plutonium with helium nuclei
  • centriole - noun one of a pair of small cylindrical cell organelles near the nucleus in animal cells; composed of nine triplet microtubules and form the asters during mitosis
  • centromere - noun a specialized condensed region of each chromosome that appears during mitosis where the chromatids are held together to form an X shape
  • centrosome - noun small region of cytoplasm adjacent to the nucleus; contains the centrioles and serves to organize the microtubules
  • cerebellum - noun a major division of the vertebrate brain; situated above the medulla oblongata and beneath the cerebrum in humans
  • cerebral cortex - noun the layer of unmyelinated neurons (the grey matter) forming the cortex of the cerebrum
  • cerebrospinal fluid - noun clear liquid produced in the ventricles of the brain; fills and protects cavities in the brain and spinal cord
  • channel - noun a passage for water (or other fluids) to flow through;a television station and its programs; a path over which electrical signals can pass; (often plural) a means of communication or access; a deep and relatively narrow body of water (as in a river or a harbor or a strait linking two larger bodies) that allows the best passage for vessels; a way of selling a company's product either directly or via distributors; a bodily passage or tube lined with epithelial cells and conveying a secretion or other substance; a long narrow furrow cut either by a natural process (such as erosion) or by a tool (as e.g. a groove in a phonograph record); verb direct the flow of; send from one person or place to another; transmit or serve as the medium for transmission
  • chaperone - noun one who accompanies and supervises a young woman or gatherings of young people; verb accompany as a chaperone
  • chelicera - noun either of the first pair of fang-like appendages near the mouth of an arachnid; often modified for grasping and piercing
  • chemical energy - noun that part of the energy in a substance that can be released by a chemical reaction
  • chemical reaction - noun (chemistry) a process in which one or more substances are changed into others
  • chitin - noun a tough semitransparent horny substance; the principal component of the exoskeletons of arthropods and the cell walls of certain fungi
  • chlorophyll - noun any of a group of green pigments found in photosynthetic organisms; there are four naturally occurring forms
  • Chlorophyll a - noun a blue-black plant pigment having a blue-green alcohol solution; found in all higher plants
  • chlorophyll a - noun a blue-black plant pigment having a blue-green alcohol solution; found in all higher plants
  • chlorophyll b - noun a dark-green plant pigment having a brilliant green alcohol solution; generally characteristic of higher plants
  • chloroplast - noun plastid containing chlorophyll and other pigments; in plants that carry out photosynthesis
  • choanocyte - noun any of the flagellated cells in sponges having a collar of cytoplasm around the flagellum; they maintain a flow of water through the body
  • Chordata - noun comprises true vertebrates and animals having a notochord
  • chorion - noun outermost membranous sac enclosing the embryo in higher vertebrates (reptiles, birds and mammals)
  • choroid plexus - noun a vascular plexus of the cerebral ventricles that regulate intraventricular pressure
  • chromatid - noun one of two identical strands into which a chromosome splits during mitosis
  • chromatin - noun the readily stainable substance of a cell nucleus consisting of DNA and RNA and various proteins; during mitotic division it condenses into chromosomes
  • chromophore - noun the chemical group that gives color to a molecule
  • Inheritance - noun hereditary succession to a title or an office or property; any attribute or immaterial possession that is inherited from ancestors; (genetics) attributes acquired via biological heredity from the parents; that which is inherited; a title or property or estate that passes by law to the heir on the death of the owner
  • chromosome - noun a threadlike body in the cell nucleus that carries the genes in a linear order
  • chylomicron - noun a microscopic particle of triglycerides produced in the intestines during digestion; in the bloodstream they release their fatty acids into the blood
  • chyme - noun a semiliquid mass of partially digested food that passes from the stomach through the pyloric sphincter into the duodenum
  • Chytridiomycetes - noun a class of mostly aquatic fungi; saprophytic or parasitic on algae or fungi or plants
  • cilium - noun a hairlike projection from the surface of a cell; provides locomotion in free-swimming unicellular organisms; any of the short curved hairs that grow from the edges of the eyelids
  • cingulate gyrus - noun a long curved structure on the medial surface of the cerebral hemispheres; the cortical part of the limbic system
  • circadian - adj. of or relating to biological processes occurring at 24-hour intervals
  • citric acid cycle - noun in all plants and animals: a series of enzymatic reactions in mitochondria involving oxidative metabolism of acetyl compounds to produce high-energy phosphate compounds that are the source of cellular energy
  • cladistics - noun a system of biological taxonomy based on the quantitative analysis of comparative data and used to reconstruct cladograms summarizing the (assumed) phylogenetic relations and evolutionary history of groups of organisms
  • class - noun elegance in dress or behavior; people having the same social or economic status; a collection of things sharing a common attribute; (biology) a taxonomic group containing one or more orders; a body of students who are taught together; a body of students who graduate together; a league ranked by quality;education imparted in a series of lessons or meetings; verb arrange or order by classes or categories
  • classical conditioning - noun conditioning that pairs a neutral stimulus with a stimulus that evokes a reflex; the stimulus that evokes the reflex is given whether or not the conditioned response occurs until eventually the neutral stimulus comes to evoke the reflex
  • clavicle - noun bone linking the scapula and sternum
  • clay - noun United States politician responsible for the Missouri Compromise between free and slave states (1777-1852); United States general who commanded United States forces in Europe from 1945 to 1949 and who oversaw the Berlin airlift (1897-1978); a very fine-grained soil that is plastic when moist but hard when fired;the dead body of a human being; water soaked soil; soft wet earth
  • cleavage - noun the act of cleaving or splitting; the line formed by a groove between two parts (especially the separation between a woman's breasts); (embryology) the repeated division of a fertilised ovum; the breaking of a chemical bond in a molecule resulting in smaller molecules; the state of being split or cleft
  • Climate - noun the weather in some location averaged over some long period of time; the prevailing psychological state
  • climate - noun the weather in some location averaged over some long period of time; the prevailing psychological state
  • cline - noun American geneticist who succeeded in transferring a functioning gene from one mouse to another (born in 1934)
  • clitoris - noun a female sexual organ homologous to the penis
  • cloaca - noun a waste pipe that carries away sewage or surface water
  • clone - noun a group of genetically identical cells or organisms derived from a single cell or individual by some kind of asexual reproduction; an unauthorized copy or imitation; a person who is almost identical to another; verb make multiple identical copies of
  • Cnidaria - noun hydras; polyps; jellyfishes; sea anemones; corals
  • cochlea - noun the snail-shaped tube (in the inner ear coiled around the modiolus) where sound vibrations are converted into nerve impulses by the organ of Corti
  • codon - noun a specific sequence of three adjacent bases on a strand of DNA or RNA that provides genetic code information for a particular amino acid
  • coelom - noun a cavity in the mesoderm of an embryo that gives rise in humans to the pleural cavity and pericardial cavity and peritoneal cavity
  • coenzyme - noun a small molecule (not a protein but sometimes a vitamin) essential for the activity of some enzymes
  • cofactor - noun a substance (as a coenzyme) that must join with another to produce a given result
  • cohesion - noun (physics) the intermolecular force that holds together the molecules in a solid or liquid; (botany) the process in some plants of parts growing together that are usually separate (such as petals); the state of cohering or sticking together
  • colloid - noun a mixture with properties between those of a solution and fine suspension
  • columella - noun a small column (or structure resembling a column) that is a part of a plant or animal
  • commensal - adj. living in a state of commensalism; noun either of two different animal or plant species living in close association but not interdependent
  • Commensalism - noun the relation between two different kinds of organisms when one receives benefits from the other without damaging it
  • commensalism - noun the relation between two different kinds of organisms when one receives benefits from the other without damaging it
  • community - noun (ecology) a group of interdependent organisms inhabiting the same region and interacting with each other; a group of people living in a particular local area; a group of people having ethnic or cultural or religious characteristics in common; a group of nations having common interests; common ownership; agreement as to goals; the body of people in a learned occupation; a district where people live; occupied primarily by private residences
  • complementary DNA - noun single-stranded DNA that is complementary to messenger RNA or DNA that has been synthesized from messenger RNA by reverse transcriptase
  • cDNA - noun single-stranded DNA that is complementary to messenger RNA or DNA that has been synthesized from messenger RNA by reverse transcriptase
  • compliance - noun happy friendly agreement; the act of submitting; usually surrendering power to another; acting according to certain accepted standards; a disposition or tendency to yield to the will of others
  • compound - adj. of leaf shapes; of leaves composed of several similar parts or lobes; consisting of two or more substances or ingredients or elements or parts; composed of many distinct individuals united to form a whole or colony; noun an enclosure of residences and other building (especially in the Orient); a whole formed by a union of two or more elements or parts; (chemistry) a substance formed by chemical union of two or more elements or ingredients in definite proportion by weight; verb put or add together;combine so as to form a whole; mix; create by mixing or combining;calculate principal and interest; make more intense, stronger, or more marked
  • compound leaf - noun a leaf composed of a number of leaflets on a common stalk
  • conclusion - noun an intuitive assumption; the last section of a communication; the proposition arrived at by logical reasoning (such as the proposition that must follow from the major and minor premises of a syllogism); a final settlement; the act of making up your mind about something; the act of ending something; a position or opinion or judgment reached after consideration; event whose occurrence ends something; the temporal end; the concluding time
  • cone - noun any cone-shaped artifact; visual receptor cell sensitive to color; cone-shaped mass of ovule- or spore-bearing scales or bracts; a shape whose base is a circle and whose sides taper up to a point; verb make cone-shaped
  • conifer - noun any gymnospermous tree or shrub bearing cones
  • conjugation - noun a class of verbs having the same inflectional forms; the complete set of inflected forms of a verb; the inflection of verbs; the act of making or becoming a single unit; the act of pairing a male and female for reproductive purposes; the state of being joined together
  • connective tissue - noun tissue of mesodermal origin consisting of e.g. collagen fibroblasts and fatty cells; supports organs and fills spaces between them and forms tendons and ligaments
  • consensus - noun agreement in the judgment or opinion reached by a group as a whole
  • contour feather - noun feathers covering the body of an adult bird and determining its shape
  • contraception - noun birth control by the use of devices (diaphragm or intrauterine device or condom) or drugs or surgery
  • control - noun the activity of managing or exerting control over something; (physiology) regulation or maintenance of a function or action or reflex etc; a mechanism that controls the operation of a machine; power to direct or determine; the economic policy of controlling or limiting or curbing prices or wages etc.; a spiritual agency that is assumed to assist the medium during a seance; a relation of constraint of one entity (thing or person or group) by another; discipline in personal and social activities; great skillfulness and knowledge of some subject or activity; a standard against which other conditions can be compared in a scientific experiment; the state that exists when one person or group has power over another;verb verify by using a duplicate register for comparison; exercise authoritative control or power over; lessen the intensity of; temper; hold in restraint; hold or keep within limits; verify or regulate by conducting a parallel experiment or comparing with another standard, of scientific experiments; have a firm understanding or knowledge of; be on top of; be careful or certain to do something; make certain of something; handle and cause to function; control (others or oneself) or influence skillfully, usually to one's advantage
  • coral reef - noun a reef consisting of coral consolidated into limestone
  • corm - noun solid swollen underground bulb-shaped stem or stem base and serving as a reproductive structure
  • cornea - noun transparent anterior portion of the outer covering of the eye; it covers the lens and iris and is continuous with the sclera
  • corolla - noun (botany) the whorl of petals of a flower that collectively form an inner floral envelope or layer of the perianth
  • corona - noun a long cigar with blunt ends; (anatomy) any structure that resembles a crown in shape; one or more circles of light seen around a luminous object; (botany) the trumpet-shaped or cup-shaped outgrowth of the corolla of a daffodil or narcissus flower; the outermost region of the sun's atmosphere; visible as a white halo during a solar eclipse; an electrical discharge accompanied by ionization of surrounding atmosphere
  • coronary artery - noun the artery that branches from the aorta to supply blood to the heart
  • corpus callosum - noun a broad transverse nerve tract connecting the two cerebral hemispheres
  • cortex - noun the tissue forming the outer layer of an organ or structure in plant or animal; the layer of unmyelinated neurons (the grey matter) forming the cortex of the cerebrum
  • cortex - noun the tissue forming the outer layer of an organ or structure in plant or animal; the layer of unmyelinated neurons (the grey matter) forming the cortex of the cerebrum
  • animal - adj. of the nature of or characteristic of or derived from an animal or animals; marked by the appetites and passions of the body; noun a living organism characterized by voluntary movement
  • Cortical - adj. of or relating to a cortex
  • corticosteroid - noun a steroid hormone produced by the adrenal cortex or synthesized; administered as drugs they reduce swelling and decrease the body's immune response
  • cortisol - noun an adrenal-cortex hormone (trade names Hydrocortone or Cortef) that is active in carbohydrate and protein metabolism
  • cotyledon - noun embryonic leaf in seed-bearing plants
  • covalent bond - noun a chemical bond that involves sharing a pair of electrons between atoms in a molecule
  • cranial nerve - noun any of the 12 paired nerves that originate in the brain stem
  • Craniata - noun fishes; amphibians; reptiles; birds; mammals
  • Craniata - noun fishes; amphibians; reptiles; birds; mammals
  • cranium - noun the part of the skull that encloses the brain
  • Crocodilia - noun crocodiles; alligators; caimans; gavials
  • crop - noun the stock or handle of a whip; the output of something in a season; a collection of people or things appearing together; a cultivated plant that is grown commercially on a large scale; the yield from plants in a single growing season; a pouch in many birds and some lower animals that resembles a stomach for storage and preliminary maceration of food; verb cut short; feed as in a meadow or pasture; let feed in a field or pasture or meadow; yield crops;cultivate, tend, and cut back the growth of; prepare for crops
  • Cross-pollination - noun stimulating influence among diverse elements; fertilization by transfer of pollen from the anthers of one flower to the stigma of another
  • cross-pollination - noun stimulating influence among diverse elements; fertilization by transfer of pollen from the anthers of one flower to the stigma of another
  • crossing over - noun the interchange of sections between pairing homologous chromosomes during the prophase of meiosis
  • crossover - noun the appropriation of a new style (especially in popular music) by combining elements of different genres in order to appeal to a wider audience; a path (often marked) where something (as a street or railroad) can be crossed to get from one side to the other; a voter who is registered as a member of one political party but who votes in the primary of another party; the interchange of sections between pairing homologous chromosomes during the prophase of meiosis
  • cryptobiosis - noun a state in which an animal's metabolic activities come to a reversible standstill
  • ctenidium - noun comb-like respiratory structure serving as the gill of certain mollusks
  • Cushing - noun United States neurologist noted for his study of the brain and pituitary gland and who identified Cushing's syndrome (1869-1939)
  • cuticle - noun the dead skin at the base of a fingernail or toenail;hard outer covering or case of certain organisms such as arthropods and turtles; the outer layer of the skin covering the exterior body surface of vertebrates
  • cuticle - noun the dead skin at the base of a fingernail or toenail;hard outer covering or case of certain organisms such as arthropods and turtles; the outer layer of the skin covering the exterior body surface of vertebrates
  • animal - adj. of the nature of or characteristic of or derived from an animal or animals; marked by the appetites and passions of the body; noun a living organism characterized by voluntary movement
  • cutting - adj. suitable for cutting or severing; as physically painful as if caused by a sharp instrument; (of speech) harsh or hurtful in tone or character; unpleasantly cold and damp; noun the act of diluting something; a piece cut off from the main part of something; a part (sometimes a root or leaf or bud) removed from a plant to propagate a new plant through rooting or grafting; the act of shortening something by choping off the ends; the act of cutting something into parts; the act of penetrating or opening open with a sharp edge; the division of a deck of cards before dealing; removing parts to create a desired shape; the activity of selecting the scenes to be shown and putting them together to create a film; an excerpt cut from a newspaper or magazine
  • cyanobacteria - noun predominantly photosynthetic prokaryotic organisms containing a blue pigment in addition to chlorophyll; occur singly or in colonies in diverse habitats; important as phytoplankton
  • cycad - noun any tropical gymnosperm of the order Cycadales; having unbranched stems with a crown of fernlike leaves
  • cAMP - adj. providing sophisticated amusement by virtue of having artificially (and vulgarly) mannered or banal or sentimental qualities;noun temporary living quarters specially built by the army for soldiers; temporary lodgings in the country for travelers or vacationers; a prison for forced laborers; a site where care and activities are provided for children during the summer months;shelter for persons displaced by war or political oppression or for religious beliefs; something that is considered amusing not because of its originality but because of its unoriginality; a group of people living together in a camp; an exclusive circle of people with a common purpose; verb give an artificially banal or sexual quality to;establish or set up a camp; live in or as if in a tent
  • cytokine - noun any of various proteins secreted by cells of the immune system that serve to regulate the immune system
  • cytokinesis - noun organic process consisting of the division of the cytoplasm of a cell following karyokinesis bringing about the separation into two daughter cells
  • Cytokinesis - noun organic process consisting of the division of the cytoplasm of a cell following karyokinesis bringing about the separation into two daughter cells
  • cytokinin - noun any of a class of plant hormones that promote cell division and delay the senescence of leaves
  • cytoplasm - noun the protoplasm of a cell excluding the nucleus; is full of proteins that control cell metabolism
  • cytoskeleton - noun a microscopic network of actin filaments and microtubules in the cytoplasm of many living cells that gives the cell shape and coherence
  • cytosol - noun the aqueous part of the cytoplasm within which various particles and organelles are suspended
  • D - noun the 4th letter of the Roman alphabet; a fat-soluble vitamin that prevents rickets
  • death rate - noun the ratio of deaths in an area to the population of that area; expressed per 1000 per year
  • D - noun the 4th letter of the Roman alphabet; a fat-soluble vitamin that prevents rickets
  • Deductive reasoning - noun reasoning from the general to the particular (or from cause to effect)
  • deductive reasoning - noun reasoning from the general to the particular (or from cause to effect)
  • degeneracy - noun the state of being degenerate in mental or moral qualities; moral perversion; impairment of virtue and moral principles
  • model - adj. worthy of imitation; noun the act of representing something (usually on a smaller scale); representation of something (sometimes on a smaller scale); a type of product; a hypothetical description of a complex entity or process; a representative form or pattern; a person who poses for a photographer or painter or sculptor; someone worthy of imitation; something to be imitated; a woman who wears clothes to display fashions; verb form in clay, wax, etc; construct a model of; create a representation or model of;plan or create according to a model or models; display (clothes) as a mannequin; assume a posture as for artistic purposes
  • demography - noun the branch of sociology that studies the characteristics of human populations
  • denature - verb make (alcohol) unfit for drinking without impairing usefulness for other purposes; modify (as a native protein) especially by heat, acid, alkali, or ultraviolet radiation so that all of the original properties are removed or diminished; add nonfissionable material to (fissionable material) so as to make unsuitable for use in an atomic bomb
  • dendrite - noun short fiber that conducts toward the cell body of the neuron
  • deoxyribonucleic acid - noun (biochemistry) a long linear polymer found in the nucleus of a cell and formed from nucleotides and shaped like a double helix; associated with the transmission of genetic information
  • DNA - noun (biochemistry) a long linear polymer found in the nucleus of a cell and formed from nucleotides and shaped like a double helix; associated with the transmission of genetic information
  • Depression - noun pushing down; sad feelings of gloom and inadequacy; angular distance below the horizon (especially of a celestial object); a concavity in a surface produced by pressing; a mental state characterized by a pessimistic sense of inadequacy and a despondent lack of activity; a long-term economic state characterized by unemployment and low prices and low levels of trade and investment; a period during the 1930s when there was a worldwide economic depression and mass unemployment; a sunken or depressed geological formation; a state of depression and anhedonia so severe as to require clinical intervention; an air mass of lower pressure; often brings precipitation
  • depression - noun pushing down; sad feelings of gloom and inadequacy; angular distance below the horizon (especially of a celestial object); a concavity in a surface produced by pressing; a mental state characterized by a pessimistic sense of inadequacy and a despondent lack of activity; a long-term economic state characterized by unemployment and low prices and low levels of trade and investment; a period during the 1930s when there was a worldwide economic depression and mass unemployment; a sunken or depressed geological formation; a state of depression and anhedonia so severe as to require clinical intervention; an air mass of lower pressure; often brings precipitation
  • Descriptive - adj. describing the structure of a language; serving to describe or inform or characterized by description; concerned with phenomena (especially language) at a particular period without considering historical antecedents
  • science - noun a particular branch of scientific knowledge; ability to produce solutions in some problem domain
  • Deuteromycota - noun large and heterogeneous form division of fungi comprising forms for which no sexually reproductive stage is known
  • diabetes insipidus - noun a rare form of diabetes resulting from a deficiency of vasopressin (the pituitary hormone that regulates the kidneys); characterized by the chronic excretion of large amounts of pale dilute urine which results in dehydration and extreme thirst
  • diabetes mellitus - noun diabetes caused by a relative or absolute deficiency of insulin and characterized by polyuria
  • DAG - noun a flap along the edge of a garment; used in medieval clothing; 10 grams
  • diaphragm - noun a mechanical device in a camera that controls size of aperture of the lens; electro-acoustic transducer that vibrates to receive or produce sound waves; a contraceptive device consisting of a flexible dome-shaped cup made of rubber or plastic; it is filled with spermicide and fitted over the uterine cervix;(anatomy) a muscular partition separating the abdominal and thoracic cavities; functions in respiration
  • diaphysis - noun the main (mid) section of a long bone
  • diapsid - noun reptile having a pair of openings in the skull behind each eye
  • diarthrosis - noun a joint so articulated as to move freely
  • diastole - noun the widening of the chambers of the heart between two contractions when the chambers fill with blood
  • Dicer - noun a mechanical device used for dicing food
  • dicot - noun flowering plant with two cotyledons; the stem grows by deposit on its outside
  • Diffusion - noun the spread of social institutions (and myths and skills) from one society to another; (physics) the process of diffusing; the intermingling of molecules in gases and liquids as a result of random thermal agitation; the act of dispersing or diffusing something; the property of being diffused or dispersed
  • diffusion - noun the spread of social institutions (and myths and skills) from one society to another; (physics) the process of diffusing; the intermingling of molecules in gases and liquids as a result of random thermal agitation; the act of dispersing or diffusing something; the property of being diffused or dispersed
  • Digestion - noun learning and coming to understand ideas and information; the organic process by which food is converted into substances that can be absorbed into the body; the process of decomposing organic matter (as in sewage) by bacteria or by chemical action or heat
  • digestion - noun learning and coming to understand ideas and information; the organic process by which food is converted into substances that can be absorbed into the body; the process of decomposing organic matter (as in sewage) by bacteria or by chemical action or heat
  • dihybrid - noun a hybrid produced by parents that differ only at two gene loci that have two alleles each
  • dimer - noun a compound whose molecules are composed of two identical monomers
  • dimorphic - adj. occurring or existing in two different forms
  • dioecious - adj. having male and female reproductive organs in separate plants or animals
  • diploid - adj. of a cell or organism having two sets of chromosomes or twice the haploid number; noun (genetics) an organism or cell having two sets of chromosomes or twice the haploid number
  • disaccharide - noun any of a variety of carbohydrates that yield two monosaccharide molecules on complete hydrolysis
  • discussion - noun an extended communication (often interactive) dealing with some particular topic; an exchange of views on some topic
  • Dispersal - noun the act of dispersing or diffusing something
  • dispersal - noun the act of dispersing or diffusing something
  • dissociation - noun the act of removing from association;(chemistry) the temporary or reversible process in which a molecule or ion is broken down into smaller molecules or ions; a state in which some integrated part of a person's life becomes separated from the rest of the personality and functions independently
  • dominant - adj. exercising influence or control; (of genes) producing the same phenotype whether its allele is identical or dissimilar; noun(music) the fifth note of the diatonic scale; an allele that produces the same phenotype whether its paired allele is identical or different
  • dormancy - noun a state of quiet (but possibly temporary) inaction;quiet and inactive restfulness
  • Dorsiflexion - noun the act of bending backward (of the body or a body part)
  • dorsiflexion - noun the act of bending backward (of the body or a body part)
  • downstream - adj. in the direction of a stream's current; adv. away from the source or with the current
  • duodenum - noun the part of the small intestine between the stomach and the jejunum
  • dura mater - noun the outermost (and toughest) of the 3 meninges
  • E - noun the 5th letter of the Roman alphabet; the base of the natural system of logarithms; approximately equal to 2.718282...; the cardinal compass point that is at 90 degrees; a radioactive transuranic element produced by bombarding plutonium with neutrons; a fat-soluble vitamin that is essential for normal reproduction; an important antioxidant that neutralizes free radicals in the body
  • eccrine gland - noun a small sweat gland the produces only a fluid; restricted to the human skin
  • ecdysis - noun periodic shedding of the cuticle in arthropods or the outer skin in reptiles
  • Echinodermata - noun radially symmetrical marine invertebrates including e.g. starfish and sea urchins and sea cucumbers
  • Ecology - noun the branch of biology concerned with the relations between organisms and their environment; the environment as it relates to living organisms
  • ecology - noun the branch of biology concerned with the relations between organisms and their environment; the environment as it relates to living organisms
  • ecosystem - noun a system formed by the interaction of a community of organisms with their physical environment
  • ectotherm - noun an animal whose body temperature varies with the temperature of its surroundings; any animal except birds and mammals
  • ectothermic - adj. of animals except birds and mammals; having body temperature that varies with the environment
  • elastase - noun a pancreatic enzyme that catalyzes the hydrolysis of elastin
  • electrocardiogram - noun a graphical recording of the cardiac cycle produced by an electrocardiograph
  • ECG - noun a graphical recording of the cardiac cycle produced by an electrocardiograph
  • electrolyte - noun a solution that conducts electricity
  • electron - noun an elementary particle with negative charge
  • electron microscope - noun a microscope that is similar in purpose to a light microscope but achieves much greater resolving power by using a parallel beam of electrons to illuminate the object instead of a beam of light
  • electronegativity - noun (chemistry) the tendency of an atom or radical to attract electrons in the formation of an ionic bond
  • electrophoresis - noun the motion of charged particles in a colloid under the influence of an electric field; particles with a positive charge go to the cathode and negative to the anode
  • element - noun the most favorable environment for a plant or animal; a straight line that generates a cylinder or cone; the situation in which you are happiest and most effective; one of four substances thought in ancient and medieval cosmology to constitute the physical universe; an artifact that is one of the individual parts of which a composite entity is made up; especially a part that can be separated from or attached to a system; an abstract part of something; any of the more than 100 known substances (of which 92 occur naturally) that cannot be separated into simpler substances and that singly or in combination constitute all matter
  • Elements - noun violent or severe weather (viewed as caused by the action of the four elements)
  • Elevation - noun drawing of an exterior of a structure; (ballet) the height of a dancer's leap or jump; distance of something above a reference point (such as sea level); the event of something being raised upward; angular distance above the horizon (especially of a celestial object); the act of increasing the wealth or prestige or power or scope of something; a raised or elevated geological formation; the highest level or degree attainable; the highest stage of development
  • elevation - noun drawing of an exterior of a structure; (ballet) the height of a dancer's leap or jump; distance of something above a reference point (such as sea level); the event of something being raised upward; angular distance above the horizon (especially of a celestial object); the act of increasing the wealth or prestige or power or scope of something; a raised or elevated geological formation; the highest level or degree attainable; the highest stage of development
  • endemic - adj. native to or confined to a certain region; of or relating to a disease (or anything resembling a disease) constantly present to greater or lesser extent in a particular locality; originating where it is found; noun a plant that is native to a certain limited area; a disease that is constantly present to a greater or lesser degree in people of a certain class or in people living in a particular location
  • endemic disease - noun a disease that is constantly present to a greater or lesser degree in people of a certain class or in people living in a particular location
  • endemism - noun nativeness by virtue or originating or occurring naturally (as in a particular place)
  • endocardium - noun the membrane that lines the cavities of the heart and forms part of the heart valves
  • endocarp - noun the hard inner (usually woody) layer of the pericarp of some fruits (as peaches or plums or cherries or olives) that contains the seed
  • endocrine - adj. of or belonging to endocrine glands or their secretions; noun any of the glands of the endocrine system that secrete hormones directly into the bloodstream; the secretion of an endocrine gland that is transmitted by the blood to the tissue on which it has a specific effect
  • endocrine gland - noun any of the glands of the endocrine system that secrete hormones directly into the bloodstream
  • endocrine system - noun the system of glands that produce endocrine secretions that help to control bodily metabolic activity
  • ER - noun a room in a hospital or clinic staffed and equipped to provide emergency care to persons requiring immediate medical treatment; a trivalent metallic element of the rare earth group; occurs with yttrium
  • endoskeleton - noun the internal skeleton; bony and cartilaginous structure (especially of vertebrates)
  • endosperm - noun nutritive tissue surrounding the embryo within seeds of flowering plants
  • enhancer - noun anything that serves by contrast to call attention to another thing's good qualities
  • enthalpy - noun (thermodynamics) a thermodynamic quantity equal to the internal energy of a system plus the product of its volume and pressure
  • entropy - noun (thermodynamics) a thermodynamic quantity representing the amount of energy in a system that is no longer available for doing mechanical work; (communication theory) a numerical measure of the uncertainty of an outcome
  • entropy - noun (thermodynamics) a thermodynamic quantity representing the amount of energy in a system that is no longer available for doing mechanical work; (communication theory) a numerical measure of the uncertainty of an outcome
  • S - noun the 19th letter of the Roman alphabet; (thermodynamics) a thermodynamic quantity representing the amount of energy in a system that is no longer available for doing mechanical work; a unit of conductance equal to the reciprocal of an ohm; the cardinal compass point that is at 180 degrees; an abundant tasteless odorless multivalent nonmetallic element; best known in yellow crystals; occurs in many sulphide and sulphate minerals and even in native form (especially in volcanic regions); 1/60 of a minute; the basic unit of time adopted under the Systeme International d'Unites
  • envelope - noun any wrapper or covering; a flat rectangular paper container for papers; the bag containing the gas in a balloon; the maximum operating capability of a system; a natural covering (as by a fluid); a curve that is tangent to each of a family of curves
  • eosinophil - noun a leukocyte readily stained with eosin
  • epicardium - noun the innermost of the two layers of the pericardium
  • epidemic - adj. (especially of medicine) of disease or anything resembling a disease; attacking or affecting many individuals in a community or a population simultaneously; noun a widespread outbreak of an infectious disease; many people are infected at the same time
  • epidermis - noun the outer layer of the skin covering the exterior body surface of vertebrates
  • epilepsy - noun a disorder of the central nervous system characterized by loss of consciousness and convulsions
  • epinephrine - noun a catecholamine secreted by the adrenal medulla in response to stress (trade name Adrenalin); stimulates autonomic nerve action
  • epiphysis - noun the end of a long bone; initially separated from the main bone by a layer of cartilage that eventually ossifies so the parts become fused; a small endocrine gland in the brain; situated beneath the back part of the corpus callosum; secretes melatonin
  • epiphyte - noun plant that derives moisture and nutrients from the air and rain; usually grows on another plant but not parasitic on it
  • epistasis - noun the suppression of a gene by the effect of an unrelated gene
  • epithelial tissue - noun membranous tissue covering internal organs and other internal surfaces of the body
  • epitope - noun the site on the surface of an antigen molecule to which an antibody attaches itself
  • equilibrium - noun a sensory system located in structures of the inner ear that registers the orientation of the head; a stable situation in which forces cancel one another; a chemical reaction and its reverse proceed at equal rates; equality of distribution
  • Equilibrium - noun a sensory system located in structures of the inner ear that registers the orientation of the head; a stable situation in which forces cancel one another; a chemical reaction and its reverse proceed at equal rates; equality of distribution
  • Erythropoietin - noun a glycoprotein secreted by the kidneys that stimulates the production of red blood cells
  • erythropoietin - noun a glycoprotein secreted by the kidneys that stimulates the production of red blood cells
  • esophagus - noun the passage between the pharynx and the stomach
  • essential - adj. basic and fundamental; absolutely required and not to be used up or sacrificed; absolutely necessary; vitally necessary;being or relating to or containing the essence of a plant etc; defining rights and duties as opposed to giving the rules by which rights and duties are established; of the greatest importance; noun anything indispensable
  • estivation - noun (botany) the arrangement of sepals and petals in a flower bud before it opens; (zoology) cessation or slowing of activity during the summer; especially slowing of metabolism in some animals during a hot or dry period
  • estrogen - noun a general term for female steroid sex hormones that are secreted by the ovary and responsible for typical female sexual characteristics
  • Estrogen - noun a general term for female steroid sex hormones that are secreted by the ovary and responsible for typical female sexual characteristics
  • estuary - noun the wide part of a river where it nears the sea; fresh and salt water mix
  • ethology - noun the branch of zoology that studies the behavior of animals in their natural habitats
  • Ethylene - noun a flammable colorless gaseous alkene; obtained from petroleum and natural gas and used in manufacturing many other chemicals; sometimes used as an anesthetic
  • ethylene - noun a flammable colorless gaseous alkene; obtained from petroleum and natural gas and used in manufacturing many other chemicals; sometimes used as an anesthetic
  • eukaryote - noun an organism with cells characteristic of all life forms except primitive microorganisms such as bacteria; i.e. an organism with `good' or membrane-bound nuclei in its cells
  • eutherian mammal - noun mammals having a placenta; all mammals except monotremes and marsupials
  • eutrophication - noun excessive nutrients in a lake or other body of water, usually caused by runoff of nutrients (animal waste, fertilizers, sewage) from the land, which causes a dense growth of plant life; the decomposition of the plants depletes the supply of oxygen, leading to the death of animal life
  • evaporation - noun the process of extracting moisture; the process of becoming a vapor
  • Eversion - noun the position of being turned outward; the act of turning inside out
  • eversion - noun the position of being turned outward; the act of turning inside out
  • evolution - noun (biology) the sequence of events involved in the evolutionary development of a species or taxonomic group of organisms; a process in which something passes by degrees to a different stage (especially a more advanced or mature stage)
  • evolutionary - adj. of or relating to or produced by evolution
  • Darwinian - adj. of or relating to Charles Darwin's theory of organic evolution; noun an advocate of Darwinism
  • fitness - noun the condition of being suitable; the quality of being qualified; good physical condition; being in shape or in condition;fitness to traverse the seas
  • exocarp - noun outermost layer of the pericarp of fruits as the skin of a peach or grape
  • exon - noun sequence of a gene's DNA that transcribes into protein structures
  • exoskeleton - noun the exterior protective or supporting structure or shell of many animals (especially invertebrates) including bony or horny parts such as nails or scales or hoofs
  • EST - noun standard time in the 5th time zone west of Greenwich, reckoned at the 75th meridian; used in the eastern United States
  • extant - adj. still in existence; not extinct or destroyed or lost
  • Extension - noun act of expanding in scope; making more widely available; act of stretching or straightening out a flexed limb; an educational opportunity provided by colleges and universities to people who not enrolled as regular students; an additional telephone set that is connected to the same telephone line; amount or degree or range to which something extends; the ability to raise the working leg high in the air; a string of characters beginning with a period and followed by one to three letters; the optional second part of a PC computer filename; a mutually agreed delay in the date set for the completion of a job or payment of a debt; an addition that extends a main building; an addition to the length of something; the most direct or specific meaning of a word or expression; the class of objects that an expression refers to; the spreading of something (a belief or practice) into new regions
  • extension - noun act of expanding in scope; making more widely available; act of stretching or straightening out a flexed limb; an educational opportunity provided by colleges and universities to people who not enrolled as regular students; an additional telephone set that is connected to the same telephone line; amount or degree or range to which something extends; the ability to raise the working leg high in the air; a string of characters beginning with a period and followed by one to three letters; the optional second part of a PC computer filename; a mutually agreed delay in the date set for the completion of a job or payment of a debt; an addition that extends a main building; an addition to the length of something; the most direct or specific meaning of a word or expression; the class of objects that an expression refers to; the spreading of something (a belief or practice) into new regions
  • extinct - adj. (of e.g. volcanos) permanently inactive; being out or having grown cold; no longer in existence; lost or especially having died out leaving no living representatives
  • extinction - noun the act of extinguishing; causing to stop burning; a conditioning process in which the reinforcer is removed and a conditioned response becomes independent of the conditioned stimulus; complete annihilation; the reduction of the intensity of radiation as a consequence of absorption and radiation; no longer in existence; no longer active; extinguished
  • F - noun the 6th letter of the Roman alphabet; the capacitance of a capacitor that has an equal and opposite charge of 1 coulomb on each plate and a voltage difference of 1 volt between the plates; a degree on the Fahrenheit scale of temperature; a nonmetallic univalent element belonging to the halogens; usually a yellow irritating toxic flammable gas; a powerful oxidizing agent; recovered from fluorite or cryolite or fluorapatite
  • F - noun the 6th letter of the Roman alphabet; the capacitance of a capacitor that has an equal and opposite charge of 1 coulomb on each plate and a voltage difference of 1 volt between the plates; a degree on the Fahrenheit scale of temperature; a nonmetallic univalent element belonging to the halogens; usually a yellow irritating toxic flammable gas; a powerful oxidizing agent; recovered from fluorite or cryolite or fluorapatite
  • F - noun the 6th letter of the Roman alphabet; the capacitance of a capacitor that has an equal and opposite charge of 1 coulomb on each plate and a voltage difference of 1 volt between the plates; a degree on the Fahrenheit scale of temperature; a nonmetallic univalent element belonging to the halogens; usually a yellow irritating toxic flammable gas; a powerful oxidizing agent; recovered from fluorite or cryolite or fluorapatite
  • FACT - noun a piece of information about circumstances that exist or events that have occurred; a concept whose truth can be proved;a statement or assertion of verified information about something that is the case or has happened; an event known to have happened or something known to have existed
  • fallout - noun the radioactive particles that settle to the ground after a nuclear explosion; any adverse and unwanted secondary effect
  • falsifiable - adj. capable of being tested (verified or falsified) by experiment or observation
  • family - noun primary social group; parents and children; people descended from a common ancestor; a social unit living together;(biology) a taxonomic group containing one or more genera; an association of people who share common beliefs or activities; a collection of things sharing a common attribute; a loose affiliation of gangsters in charge of organized criminal activities; a person having kinship with another or others
  • Fecundity - noun the intellectual productivity of a creative imagination; the quality of something that causes or assists healthy growth; the state of being fertile; capable of producing offspring
  • fecundity - noun the intellectual productivity of a creative imagination; the quality of something that causes or assists healthy growth; the state of being fertile; capable of producing offspring
  • femur - noun the longest and thickest bone of the human skeleton; extends from the pelvis to the knee
  • fermentation - noun a process in which an agent causes an organic substance to break down into simpler substances; especially, the anaerobic breakdown of sugar into alcohol; a state of agitation or turbulent change or development
  • fern - noun any of numerous flowerless and seedless vascular plants having true roots from a rhizome and fronds that uncurl upward; reproduce by spores
  • fertilization - noun making fertile as by applying fertilizer or manure;creation by the physical union of male and female gametes; of sperm and ova in an animal or pollen and ovule in a plant
  • fibula - noun the outer and thinner of the two bones of the human leg between the knee and ankle
  • field - noun a particular kind of commercial enterprise; the area that is visible (as through an optical instrument); all the competitors in a particular contest or sporting event; all of the horses in a particular horse race; (mathematics) a set of elements such that addition and multiplication are commutative and associative and multiplication is distributive over addition and there are two elements 0 and 1;(computer science) a set of one or more adjacent characters comprising a unit of information; a region in which active military operations are in progress; somewhere (away from a studio or office or library or laboratory) where practical work is done or data is collected; a piece of land cleared of trees and usually enclosed; a geographic region (land or sea) under which something valuable is found; the space around a radiating body within which its electromagnetic oscillations can exert force on another similar body not in contact with it; a place where planes take off and land; a branch of knowledge; a region where a battle is being (or has been) fought; a piece of land prepared for playing a game; extensive tract of level open land; a particular environment or walk of life; verbselect (a team or individual player) for a game; answer adequately or successfully; play as a fielder; catch or pick up (balls) in baseball or cricket
  • filament - noun a thin wire (usually tungsten) that is heated white hot by the passage of an electric current; a threadlike structure (as a chainlike series of cells); the stalk of a stamen; a very slender natural or synthetic fiber
  • Fission - noun a nuclear reaction in which a massive nucleus splits into smaller nuclei with the simultaneous release of energy;reproduction of some unicellular organisms by division of the cell into two more or less equal parts
  • fission - noun a nuclear reaction in which a massive nucleus splits into smaller nuclei with the simultaneous release of energy;reproduction of some unicellular organisms by division of the cell into two more or less equal parts
  • fixation - noun (histology) the preservation and hardening of a tissue sample to retain as nearly as possible the same relations they had in the living body; the activity of fastening something firmly in position; an unhealthy and compulsive preoccupation with something or someone; an abnormal state in which development has stopped prematurely
  • flagellum - noun a lash-like appendage used for locomotion (e.g., in sperm cells and some bacteria and protozoa); a whip used to inflict punishment (often used for pedantic humor)
  • flat bone - noun part of the sirloin next to the wedge bone
  • Flexion - noun act of bending a joint; especially a joint between the bones of a limb so that the angle between them is decreased;deviation from a straight or normal course; the state of being flexed (as of a joint)
  • flexion - noun act of bending a joint; especially a joint between the bones of a limb so that the angle between them is decreased;deviation from a straight or normal course; the state of being flexed (as of a joint)
  • flight feather - noun any of the larger wing or tail feathers of a bird
  • flower - noun reproductive organ of angiosperm plants especially one having showy or colorful parts; a plant cultivated for its blooms or blossoms; the period of greatest prosperity or productivity; verbproduce or yield flowers
  • foot - noun travel by walking; any of various organs of locomotion or attachment in invertebrates; a support resembling a pedal extremity;the part of the leg of a human being below the ankle joint; the lower part of anything; a member of a surveillance team who works on foot or rides as a passenger; a linear unit of length equal to 12 inches or a third of a yard; the pedal extremity of vertebrates other than human beings; lowest support of a structure; (prosody) a group of 2 or 3 syllables forming the basic unit of poetic rhythm; an army unit consisting of soldiers who fight on foot; verb add a column of numbers; walk; pay for something
  • Foraging - noun the act of searching for food and provisions
  • foraging - noun the act of searching for food and provisions
  • forearm - noun the part of the superior limb between the elbow and the wrist; verb arm in advance of a confrontation
  • fovea - noun area consisting of a small depression in the retina containing cones and where vision is most acute
  • fragmentation - noun the scattering of bomb fragments after the bomb explodes; (computer science) the condition of a file that is broken up and stored in many different locations on a magnetic disk;the disintegration of social norms governing behavior and thought and social relationships; separating something into fine particles
  • Fragmentation - noun the scattering of bomb fragments after the bomb explodes; (computer science) the condition of a file that is broken up and stored in many different locations on a magnetic disk;the disintegration of social norms governing behavior and thought and social relationships; separating something into fine particles
  • free nerve ending - noun microscopic sensory nerve endings in the skin that are not connected to any specific sensory receptor
  • frog - noun any of various tailless stout-bodied amphibians with long hind limbs for leaping; semiaquatic and terrestrial species; a decorative loop of braid or cord; a person of French descent; verbhunt frogs for food
  • frontal - adj. belonging to the front part; of or adjacent to the forehead or frontal bone; meeting front to front; of or relating to the front of an advancing mass of air; noun a drapery that covers the front of an altar; the face or front of a building; an adornment worn on the forehead
  • coronal - noun flower arrangement consisting of a circular band of foliage or flowers for ornamental purposes
  • plane - adj. having a surface without slope, tilt in which no part is higher or lower than another; noun a carpenter's hand tool with an adjustable blade for smoothing or shaping wood; a power tool for smoothing or shaping wood; (mathematics) an unbounded two-dimensional shape; a level of existence or development; an aircraft that has a fixed wing and is powered by propellers or jets; verb cut or remove with or as if with a plane; make even or smooth, with or as with a carpenter's plane; travel on the surface of water
  • frontal lobe - noun that part of the cerebral cortex in either hemisphere of the brain lying directly behind the forehead
  • fruit - noun the consequence of some effort or action; the ripened reproductive body of a seed plant; an amount of a product; verbbear fruit; cause to bear fruit
  • furcula - noun a forked bone formed by the fusion of the clavicles of most birds
  • fusion - noun the act of fusing (or melting) together; correction of an unstable part of the spine by joining two or more vertebrae; usually done surgically but sometimes done by traction or immobilization;the combining of images from the two eyes to form a single visual percept; an occurrence that involves the production of a union; a nuclear reaction in which nuclei combine to form more massive nuclei with the simultaneous release of energy; the merging of adjacent sounds or syllables or words; the state of being combined into one body
  • G - noun the 7th letter of the Roman alphabet; a unit of force equal to the force exerted by gravity; used to indicate the force to which a body is subjected when it is accelerated; (physics) the universal constant relating force to mass and distance in Newton's law of gravitation; a unit of information equal to one billion (1,073,741,824) bytes or 1024 megabytes; a metric unit of weight equal to one thousandth of a kilogram; one of the four nucleotides used in building DNA; all four nucleotides have a common phosphate group and a sugar (ribose); a purine base found in DNA and RNA; pairs with cytosine
  • gall - noun abnormal swelling of plant tissue caused by insects or microorganisms or injury; a skin sore caused by chafing; the trait of being rude and impertinent; inclined to take liberties; a digestive juice secreted by the liver and stored in the gallbladder; aids in the digestion of fats; a feeling of deep and bitter anger and ill-will; an open sore on the back of a horse caused by ill-fitting or badly adjusted saddle; verb irritate or vex; become or make sore by or as if by rubbing
  • gallbladder - noun a muscular sac attached to the liver that secretes bile and stores it until needed for digestion
  • gametangium - noun cell or organ in which gametes develop
  • gamete - noun a mature sexual reproductive cell having a single set of unpaired chromosomes
  • gametophyte - noun the gamete-bearing individual or phase in the life cycle of a plant having alternation of generations
  • gastrin - noun polypeptide hormone secreted by the mucous lining of the stomach; induces the secretion of gastric juice
  • gastrula - noun double-walled stage of the embryo resulting from invagination of the blastula; the outer layer of cells is the ectoderm and the inner layer differentiates into the mesoderm and endoderm
  • Gastrulation - noun the process in which a gastrula develops from a blastula by the inward migration of cells
  • gastrulation - noun the process in which a gastrula develops from a blastula by the inward migration of cells
  • gemma - noun small asexual reproductive structure in e.g. liverworts and mosses that detaches from the parent and develops into a new individual
  • gene - noun (genetics) a segment of DNA that is involved in producing a polypeptide chain; it can include regions preceding and following the coding DNA as well as introns between the exons; it is considered a unit of heredity
  • gene expression - noun conversion of the information encoded in a gene first into messenger RNA and then to a protein
  • Genetic engineering - noun the technology of preparing recombinant DNA in vitro by cutting up DNA molecules and splicing together fragments from more than one organism
  • genetic engineering - noun the technology of preparing recombinant DNA in vitro by cutting up DNA molecules and splicing together fragments from more than one organism
  • genetic map - noun graphical representation of the arrangement of genes on a chromosome
  • genetic marker - noun a specific gene that produces a recognizable trait and can be used in family or population studies
  • genome - noun the ordering of genes in a haploid set of chromosomes of a particular organism; the full DNA sequence of an organism
  • Genomics - noun the branch of genetics that studies organisms in terms of their genomes (their full DNA sequences)
  • genomics - noun the branch of genetics that studies organisms in terms of their genomes (their full DNA sequences)
  • genotype - noun the particular alleles at specified loci present in an organism; a group of organisms sharing a specific genetic constitution
  • genus - noun a general kind of something; (biology) taxonomic group containing one or more species
  • germ layer - noun (embryology) any of the 3 layers of cells differentiated in embryos following gastrulation
  • gestation - noun the conception and development of an idea or plan; the period during which an embryo develops (about 266 days in humans); the state of being pregnant; the period from conception to birth when a woman carries a developing fetus in her uterus
  • gibberellin - noun a plant hormone isolated from a fungus; used in promoting plant growth
  • GA - noun a state in southeastern United States; one of the Confederate states during the American Civil War; a rare silvery (usually trivalent) metallic element; brittle at low temperatures but liquid above room temperature; occurs in trace amounts in bauxite and zinc ores; the first known nerve agent, synthesized by German chemists in 1936; a highly toxic combustible liquid that is soluble in organic solvents and is used as a nerve gas in chemical warfare
  • gigantism - noun excessive largeness of stature; excessive size; usually caused by excessive secretion of growth hormone from the pituitary gland
  • gizzard - noun thick-walled muscular pouch below the crop in many birds and reptiles for grinding food
  • glabrous - adj. having no hair or similar growth; smooth
  • glia - noun sustentacular tissue that surrounds and supports neurons in the central nervous system; glial and neural cells together compose the tissue of the central nervous system
  • glomerulus - noun a small intertwined group of capillaries in the malpighian body; it filters the blood during urine formation
  • glomerulus - noun a small intertwined group of capillaries in the malpighian body; it filters the blood during urine formation
  • renal - adj. of or relating to the kidneys
  • glucagon - noun a hormone secreted by the pancreas; stimulates increases in blood sugar levels in the blood (thus opposing the action of insulin)
  • glucocorticoid - noun a steroid hormone that is produced by the adrenal cortex of animals; affects functioning of gonads and has anti-inflammatory activity
  • GLUT - noun the quality of being so overabundant that prices fall;verb overeat or eat immodestly; make a pig of oneself; supply with an excess of
  • Glycogen - noun one form in which body fuel is stored; stored primarily in the liver and broken down into glucose when needed by the body
  • glycogen - noun one form in which body fuel is stored; stored primarily in the liver and broken down into glucose when needed by the body
  • Glycolysis - noun a metabolic process that breaks down carbohydrates and sugars through a series of reactions to either pyruvic acid or lactic acid and release energy for the body in the form of ATP
  • glycolysis - noun a metabolic process that breaks down carbohydrates and sugars through a series of reactions to either pyruvic acid or lactic acid and release energy for the body in the form of ATP
  • glycoprotein - noun a conjugated protein having a carbohydrate component
  • gnathostome - noun a vertebrate animal possessing true jaws
  • goiter - noun abnormally enlarged thyroid gland; can result from underproduction or overproduction of hormone or from a deficiency of iodine in the diet
  • Golgi apparatus - noun a netlike structure in the cytoplasm of animal cells (especially in those cells that produce secretions)
  • gonadotropin - noun hormone secreted by the anterior pituitary gland and placenta; stimulates the gonads and controls reproductive activity
  • hormone - noun the secretion of an endocrine gland that is transmitted by the blood to the tissue on which it has a specific effect
  • Gorilla - noun largest anthropoid ape; terrestrial and vegetarian; of forests of central west Africa
  • grafting - noun the act of grafting something onto something else
  • Gram-negative - adj. (of bacteria) being of or relating to a bacterium that does not retain the violet stain used in Gram's method
  • Gram-positive - adj. (of bacteria) being or relating to a bacterium that retains the violet stain used in Gram's method
  • Great Barrier Reef - noun the largest coral reef in the world; in the Coral Sea off the northeastern coast of Australia
  • greenhouse effect - noun warming that results when solar radiation is trapped by the atmosphere; caused by atmospheric gases that allow sunshine to pass through but absorb heat that is radiated back from the warmed surface of the earth
  • growth factor - noun a protein that is involved in cell differentiation and growth
  • Growth hormone - noun a hormone produced by the anterior pituitary gland; promotes growth in humans
  • growth hormone - noun a hormone produced by the anterior pituitary gland; promotes growth in humans
  • hormone - noun the secretion of an endocrine gland that is transmitted by the blood to the tissue on which it has a specific effect
  • hormone - noun the secretion of an endocrine gland that is transmitted by the blood to the tissue on which it has a specific effect
  • GDP - noun measure of the United States economy adopted in 1991; the total market values of goods and services by produced by workers and capital within the United States borders during a given period (usually 1 year)
  • gustation - noun the faculty of distinguishing sweet, sour, bitter, and salty properties in the mouth
  • gymnosperm - noun plants of the class Gymnospermae having seeds not enclosed in an ovary
  • gyrus - noun a convex fold or elevation in the surface of the brain
  • H - noun the 8th letter of the Roman alphabet; (thermodynamics) a thermodynamic quantity equal to the internal energy of a system plus the product of its volume and pressure; the constant of proportionality relating the energy of a photon to its frequency; approximately 6.626 x 10^-34 joule-second; a unit of inductance in which an induced electromotive force of one volt is produced when the current is varied at the rate of one ampere per second; a nonmetallic univalent element that is normally a colorless and odorless highly flammable diatomic gas; the simplest and lightest and most abundant element in the universe
  • Habituation - noun a general accommodation to unchanging environmental conditions; being abnormally tolerant to and dependent on something that is psychologically or physically habit-forming (especially alcohol or narcotic drugs)
  • habituation - noun a general accommodation to unchanging environmental conditions; being abnormally tolerant to and dependent on something that is psychologically or physically habit-forming (especially alcohol or narcotic drugs)
  • hagfish - noun eellike cyclostome having a tongue with horny teeth in a round mouth surrounded by eight tentacles; feeds on dead or trapped fishes by boring into their bodies
  • hair - noun a filamentous projection or process on an organism; any of the cylindrical filaments characteristically growing from the epidermis of a mammal; a covering for the body (or parts of it) consisting of a dense growth of threadlike structures (as on the human head); helps to prevent heat loss; filamentous hairlike growth on a plant; cloth woven from horsehair or camelhair; used for upholstery or stiffening in garments; a very small distance or space
  • hairpin - noun a double pronged pin used to hold women's hair in place
  • halophile - noun archaebacteria requiring a salt-rich environment for growth and survival
  • haploid - adj. of a cell or organism having a single set of chromosomes; noun (genetics) an organism or cell having only one complete set of chromosomes
  • Haversian canal - noun any of the many tiny canals that contain blood vessels and connective tissue and that form a network in bone
  • heat - noun the trait of being intensely emotional; the sensation caused by heat energy; a preliminary race in which the winner advances to a more important race; a form of energy that is transferred by a difference in temperature; utility to warm a building;the presence of heat; applies to nonhuman mammals: a state or period of heightened sexual arousal and activity; verb make hot or hotter; gain heat or get hot; provide with heat; arouse or excite feelings and passions
  • Heat energy - noun a form of energy that is transferred by a difference in temperature
  • heat energy - noun a form of energy that is transferred by a difference in temperature
  • heat of vaporization - noun heat absorbed by a unit mass of a material at its boiling point in order to convert the material into a gas at the same temperature
  • TH - noun a soft silvery-white tetravalent radioactive metallic element; isotope 232 is used as a power source in nuclear reactors; occurs in thorite and in monazite sands; the fifth day of the week; the fourth working day
  • TH - noun a soft silvery-white tetravalent radioactive metallic element; isotope 232 is used as a power source in nuclear reactors; occurs in thorite and in monazite sands; the fifth day of the week; the fourth working day
  • Hemoglobin - noun a hemoprotein composed of globin and heme that gives red blood cells their characteristic color; function primarily to transport oxygen from the lungs to the body tissues
  • hemoglobin - noun a hemoprotein composed of globin and heme that gives red blood cells their characteristic color; function primarily to transport oxygen from the lungs to the body tissues
  • herbaceous - adj. characteristic of a nonwoody herb or plant part
  • herbivore - noun any animal that feeds chiefly on grass and other plants
  • hermaphrodite - adj. of animal or plant; having both male female reproductive organs; noun one having both male and female sexual characteristics and organs; at birth an unambiguous assignment of male or female cannot be made
  • Hermaphroditism - noun congenital condition in which external genitalia and internal sex organs have both male and female characteristics; showing characteristics of both sexes
  • hermaphroditism - noun congenital condition in which external genitalia and internal sex organs have both male and female characteristics; showing characteristics of both sexes
  • heterogeneity - noun the quality of being diverse and not comparable in kind
  • heterotroph - noun an organism that depends on complex organic substances for nutrition
  • heterozygous - adj. having dissimilar alleles at corresponding chromosomal loci
  • hibernation - noun the act of retiring into inactivity; cessation from or slowing of activity during the winter; especially slowing of metabolism in some animals; the torpid or resting state in which some animals pass the winter
  • Hibernation - noun the act of retiring into inactivity; cessation from or slowing of activity during the winter; especially slowing of metabolism in some animals; the torpid or resting state in which some animals pass the winter
  • hilum - noun the scar on certain seeds marking its point of attachment to the funicle; (anatomy) a depression or fissure where vessels or nerves or ducts enter a bodily organ
  • hinge joint - noun a freely moving joint in which the bones are so articulated as to allow extensive movement in one plane; a joint allowing movement in one plane only
  • hippocampus - noun seahorses; a complex neural structure (shaped like a sea horse) consisting of grey matter and located on the floor of each lateral ventricle; intimately involved in motivation and emotion as part of the limbic system; has a central role in the formation of memories
  • histone - noun a simple protein containing mainly basic amino acids; present in cell nuclei in association with nucleic acids
  • HIV - noun infection by the human immunodeficiency virus; the virus that causes acquired immune deficiency syndrome (AIDS); it replicates in and kills the helper T cells
  • virus - noun (virology) ultramicroscopic infectious agent that replicates itself only within cells of living hosts; many are pathogenic; a piece of nucleic acid (DNA or RNA) wrapped in a thin coat of protein; a software program capable of reproducing itself and usually capable of causing great harm to files or other programs on the same computer; a harmful or corrupting agency
  • homeostasis - noun (physiology) metabolic equilibrium actively maintained by several complex biological mechanisms that operate via the autonomic nervous system to offset disrupting changes
  • Homeostasis - noun (physiology) metabolic equilibrium actively maintained by several complex biological mechanisms that operate via the autonomic nervous system to offset disrupting changes
  • hominoid - noun a primate of the superfamily Hominoidea
  • Homo - noun any living or extinct member of the family Hominidae characterized by superior intelligence, articulate speech, and erect carriage; someone who practices homosexuality; having a sexual attraction to persons of the same sex
  • homologous - adj. corresponding or similar in position or structure or function or characteristics; especially derived from an organism of the same species; having the same evolutionary origin but serving different functions
  • homozygous - adj. having identical alleles at corresponding chromosomal loci
  • horizon - noun the range of interest or activity that can be anticipated; the line at which the sky and Earth appear to meet; the great circle on the celestial sphere whose plane passes through the sensible horizon and the center of the Earth; a specific layer or stratum of soil or subsoil in a vertical cross section of land
  • hormone - noun the secretion of an endocrine gland that is transmitted by the blood to the tissue on which it has a specific effect
  • horsetail - noun perennial rushlike flowerless herbs with jointed hollow stems and narrow toothlike leaves that spread by creeping rhizomes; tend to become weedy; common in northern hemisphere; some in Africa and South America
  • host - noun an animal or plant that nourishes and supports a parasite; it does not benefit and is often harmed by the association;a technical name for the bread used in the service of Mass or Holy Communion; archaic terms for army; any organization that provides resources and facilities for a function or event; the owner or manager of an inn; a person who invites guests to a social event (such as a party in his or her own home) and who is responsible for them while they are there; (medicine) recipient of transplanted tissue or organ from a donor; (computer science) a computer that provides client stations with access to files and printers as shared resources to a computer network; a vast multitude; a person who acts as host at formal occasions (makes an introductory speech and introduces other speakers); verb be the host of or for
  • gonadotropin - noun hormone secreted by the anterior pituitary gland and placenta; stimulates the gonads and controls reproductive activity
  • HCG - noun hormone produced early in pregnancy by the placenta; detection in the urine and serum is the basis for one kind of pregnancy test
  • human growth hormone - noun a hormone produced by the anterior pituitary gland; promotes growth in humans
  • humerus - noun bone extending from the shoulder to the elbow
  • humus - noun partially decomposed organic matter; the organic component of soil; a thick spread made from mashed chickpeas, tahini, lemon juice and garlic; used especially as a dip for pita; originated in the Middle East
  • hybrid - adj. produced by crossbreeding; noun an organism that is the offspring of genetically dissimilar parents or stock; especially offspring produced by breeding plants or animals of different varieties or breeds or species; a composite of mixed origin; a word that is composed of parts from different languages (e.g., `monolingual' has a Greek prefix and a Latin root)
  • hybridization - noun (genetics) the act of mixing different species or varieties of animals or plants and thus to produce hybrids
  • hydrocarbon - noun an organic compound containing only carbon and hydrogen
  • hydrogen bond - noun a chemical bond consisting of a hydrogen atom between two electronegative atoms (e.g., oxygen or nitrogen) with one side be a covalent bond and the other being an ionic bond
  • hydrolysis - noun a chemical reaction in which water reacts with a compound to produce other compounds; involves the splitting of a bond and the addition of the hydrogen cation and the hydroxide anion from the water
  • hydrophilic - adj. having a strong affinity for water; tending to dissolve in, mix with, or be wetted by water
  • hydrophobic - adj. abnormally afraid of water; lacking affinity for water; tending to repel and not absorb water; tending not to dissolve in or mix with or be wetted by water
  • Hydrophobic - adj. abnormally afraid of water; lacking affinity for water; tending to repel and not absorb water; tending not to dissolve in or mix with or be wetted by water
  • hydrosphere - noun the watery layer of the earth's surface; includes water vapor
  • Hylobatidae - noun used in some classifications for the lesser apes (gibbons and siamangs); sometimes considered a subfamily of Pongidae
  • hyoid bone - noun a U-shaped bone at the base of the tongue that supports the tongue muscles
  • hyperglycemia - noun abnormally high blood sugar usually associated with diabetes
  • hyperopia - noun abnormal condition in which vision for distant objects is better than for near objects
  • hyperplasia - noun abnormal increase in number of cells
  • Hyperthyroidism - noun an overactive thyroid gland; pathologically excessive production of thyroid hormones or the condition resulting from excessive production of thyroid hormones
  • hyperthyroidism - noun an overactive thyroid gland; pathologically excessive production of thyroid hormones or the condition resulting from excessive production of thyroid hormones
  • hypertonic - adj. (of a solution) having a higher osmotic pressure than a comparison solution; (of living tissue) in a state of abnormally high tension
  • hypha - noun any of the threadlike filaments forming the mycelium of a fungus
  • hypoglycemia - noun abnormally low blood sugar usually resulting from excessive insulin or a poor diet
  • Hypothyroidism - noun an underactive thyroid gland; a glandular disorder resulting from insufficient production of thyroid hormones
  • hypothyroidism - noun an underactive thyroid gland; a glandular disorder resulting from insufficient production of thyroid hormones
  • hypotonic - adj. (of a solution) having a lower osmotic pressure than a comparison solution; (of living tissue) lacking normal tone or tension
  • I - noun the 9th letter of the Roman alphabet; a nonmetallic element belonging to the halogens; used especially in medicine and photography and in dyes; occurs naturally only in combination in small quantities (as in sea water or rocks)
  • ileum - noun the part of the small intestine between the jejunum and the cecum
  • Immunodeficiency - noun immunological disorder in which some part of the body's immune system is inadequate and resistance to infectious diseases is reduced
  • immunodeficiency - noun immunological disorder in which some part of the body's immune system is inadequate and resistance to infectious diseases is reduced
  • Imprinting - noun a learning process in early life whereby species specific patterns of behavior are established
  • imprinting - noun a learning process in early life whereby species specific patterns of behavior are established
  • inbreeding - noun the act of mating closely related individuals
  • incus - noun the ossicle between the malleus and the stapes
  • inert - adj. slow and apathetic; unable to move or resist motion;having only a limited ability to react chemically; chemically inactive
  • inert gas - noun any of the chemically inert gaseous elements of the helium group in the periodic table
  • inferior vena cava - noun receives blood from lower limbs and abdominal organs and empties into the posterior part of the right atrium of the heart; formed from the union of the two iliac veins
  • Infertility - noun the state of being unable to produce offspring; in a woman it is an inability to conceive; in a man it is an inability to impregnate
  • infertility - noun the state of being unable to produce offspring; in a woman it is an inability to conceive; in a man it is an inability to impregnate
  • inflammation - noun arousal to violent emotion; a response of body tissues to injury or irritation; characterized by pain and swelling and redness and heat; the act of setting something on fire; the state of being emotionally aroused and worked up
  • ingestion - noun the process of taking food into the body through the mouth (as by eating)
  • inhibitor - noun a substance that retards or stops an activity
  • Innate immunity - noun immunity to disease that occurs as part of an individual's natural biologic makeup
  • innate immunity - noun immunity to disease that occurs as part of an individual's natural biologic makeup
  • inner ear - noun a complex system of interconnecting cavities; concerned with hearing and equilibrium
  • IP - noun the sciences concerned with gathering, manipulating, storing, retrieving, and classifying recorded information
  • IC - noun a group of government agencies and organizations that carry out intelligence activities for the United States government; headed by the Director of Central Intelligence
  • Insulin - noun hormone secreted by the isles of Langerhans in the pancreas; regulates storage of glycogen in the liver and accelerates oxidation of sugar in cells
  • insulin - noun hormone secreted by the isles of Langerhans in the pancreas; regulates storage of glycogen in the liver and accelerates oxidation of sugar in cells
  • integument - noun an outer protective covering such as the skin of an animal or a cuticle or seed coat or rind or shell
  • interferon - noun an antiviral protein produced by cells that have been invaded by a virus; inhibits replication of the virus
  • intermittent - adj. stopping and starting at irregular intervals;stopping and starting at regular intervals
  • internode - noun a segment of a stem between two nodes
  • interstitial fluid - noun liquid found between the cells of the body that provides much of the liquid environment of the body
  • intervertebral disc - noun a fibrocartilaginous disc serving as a cushion between all of the vertebrae of the spinal column (except between the first two)
  • introduction - noun the act of beginning something new; the first section of a communication; a basic or elementary instructional text;a new proposal; the act of starting something for the first time; introducing something new; the act of putting one thing into another;formally making a person known to another or to the public
  • intron - noun sequence of a eukaryotic gene's DNA that is not translated into a protein
  • Inversion - noun the act of turning inside out; turning upside down; setting on end; a term formerly used to mean taking on the gender role of the opposite sex; (counterpoint) a variation of a melody or part in which ascending intervals are replaced by descending intervals and vice versa; (genetics) a kind of mutation in which the order of the genes in a section of a chromosome is reversed; the layer of air near the earth is cooler than an overlying layer; a chemical process in which the direction of optical rotation of a substance is reversed from dextrorotatory to levorotary or vice versa; abnormal condition in which an organ is turned inward or inside out (as when the upper part of the uterus is pulled into the cervical canal after childbirth); the reversal of the normal order of words
  • inversion - noun the act of turning inside out; turning upside down; setting on end; a term formerly used to mean taking on the gender role of the opposite sex; (counterpoint) a variation of a melody or part in which ascending intervals are replaced by descending intervals and vice versa; (genetics) a kind of mutation in which the order of the genes in a section of a chromosome is reversed; the layer of air near the earth is cooler than an overlying layer; a chemical process in which the direction of optical rotation of a substance is reversed from dextrorotatory to levorotary or vice versa; abnormal condition in which an organ is turned inward or inside out (as when the upper part of the uterus is pulled into the cervical canal after childbirth); the reversal of the normal order of words
  • ion - noun a particle that is electrically charged (positive or negative); an atom or molecule or group that has lost or gained one or more electrons
  • iris - noun diaphragm consisting of thin overlapping plates that can be adjusted to change the diameter of a central opening; muscular diaphragm that controls the size of the pupil; it forms the colored portion of the eye; plants with sword-shaped leaves and erect stalks bearing bright-colored flowers composed of three petals and three drooping sepals
  • islets of Langerhans - noun cell clusters in the pancreas that form the endocrine part of that organ; secrete insulin and other hormones
  • islets of Langerhans - noun cell clusters in the pancreas that form the endocrine part of that organ; secrete insulin and other hormones
  • isomerase - noun an enzyme that catalyzes its substrate to an isomeric form
  • isotonic - adj. of or involving muscular contraction in which tension is constant while length changes; (used of solutions) having the same or equal osmotic pressure; of two or more muscles; having equal tension; relating to or characterized by the equal intervals of a musical scale
  • isotope - noun one of two or more atoms with the same atomic number but with different numbers of neutrons
  • isthmus - noun a cord-like tissue connecting two larger parts of an anatomical structure; a relatively narrow strip of land (with water on both sides) connecting two larger land areas
  • J - noun the 10th letter of the Roman alphabet; a unit of electrical energy equal to the work done when a current of one ampere passes through a resistance of one ohm for one second
  • jejunum - noun the part of the small intestine between the duodenum and the ileum
  • joint - adj. involving both houses of a legislature; united or combined; affecting or involving two or more; noun marijuana leaves rolled into a cigarette for smoking; junction by which parts or objects are joined together; a disreputable place of entertainment;(anatomy) the point of connection between two bones or elements of a skeleton (especially if it allows motion); a piece of meat roasted or for roasting and of a size for slicing into more than one portion; the shape or manner in which things come together and a connection is made; verb separate (meat) at the joint; fasten with a joint; provide with a joint; fit as if by joints
  • K - noun street names for ketamine; the 11th letter of the Roman alphabet; a unit of information equal to one thousand (1024) bytes;the basic unit of thermodynamic temperature adopted under the Systeme International d'Unites; a light soft silver-white metallic element of the alkali metal group; oxidizes rapidly in air and reacts violently with water; is abundant in nature in combined forms occurring in sea water and in carnallite and kainite and sylvite
  • karyokinesis - noun organic process consisting of the division of the nucleus of a cell during mitosis or meiosis
  • karyotype - noun the appearance of the chromosomal makeup of a somatic cell in an individual or species (including the number and arrangement and size and structure of the chromosomes)
  • keratin - noun a fibrous scleroprotein that occurs in the outer layer of the skin and in horny tissues such as hair feathers nails and hooves
  • kidney - noun either of two bean-shaped excretory organs that filter wastes (especially urea) from the blood and excrete them and water in urine
  • kinase - noun an enzyme that catalyzes the conversion of a proenzyme to an active enzyme
  • kinesis - noun a movement that is a response to a stimulus but is not oriented with respect to the source of stimulation
  • kinesthesia - noun the perception of body position and movement and muscular tensions etc; the ability to feel movements of the limbs and body
  • kinetic energy - noun the mechanical energy that a body has by virtue of its motion
  • kinetochore - noun a specialized condensed region of each chromosome that appears during mitosis where the chromatids are held together to form an X shape
  • kingdom - noun a basic group of natural objects; the highest taxonomic group into which organisms are grouped; one of five biological categories: Monera or Protoctista or Plantae or Fungi or Animalia; a monarchy with a king or queen as head of state; the domain ruled by a king or queen; a country with a king as head of state; a domain in which something is dominant
  • Krebs cycle - noun in all plants and animals: a series of enzymatic reactions in mitochondria involving oxidative metabolism of acetyl compounds to produce high-energy phosphate compounds that are the source of cellular energy
  • L - noun the 12th letter of the Roman alphabet; a metric unit of capacity equal to the volume of 1 kilogram of pure water at 4 degrees centigrade and 760 mm of mercury (or approximately 1.76 pints); a cgs unit of illumination equal to the brightness of a perfectly diffusing surface that emits or reflects one lumen per square centimeter
  • labyrinth - noun complex system of paths or tunnels in which it is easy to get lost; a complex system of interconnecting cavities; concerned with hearing and equilibrium
  • lactase - noun any of a group of enzymes (trade name Lactaid) that hydrolyze lactose to glucose and galactose
  • lacuna - noun a blank gap or missing part; an ornamental sunken panel in a ceiling or dome
  • lamella - noun thin plate; a thin membrane that is one of the calcified layers that form bones; any of the radiating leaflike spore-producing structures on the underside of the cap of a mushroom or similar fungus
  • lamina - noun a thin plate or layer (especially of bone or mineral)
  • lamprey - noun primitive eellike freshwater or anadromous cyclostome having round sucking mouth with a rasping tongue
  • lancelet - noun small translucent lancet-shaped burrowing marine animal; primitive forerunner of the vertebrates
  • large intestine - noun beginning with the cecum and ending with the rectum; includes the cecum and the colon and the rectum; extracts moisture from food residues which are later excreted as feces
  • larynx - noun a cartilaginous structure at the top of the trachea; contains elastic vocal cords that are the source of the vocal tone in speech
  • latency - noun the state of being not yet evident or active; the time that elapses between a stimulus and the response to it; (computer science) the time it takes for a specific block of data on a data track to rotate around to the read/write head
  • lateral line - noun sense organs of fish and amphibians; believed to detect pressure changes in the water
  • Laurasia - noun a hypothetical continent that (according to plate tectonic theory) broke up later into North America and Europe and Asia
  • law of independent assortment - noun each member of a pair of homologous chromosomes separates independently of the members of other pairs so the results are random
  • law of mass action - noun (chemistry) the law that states the following principle: the rate of a chemical reaction is directly proportional to the molecular concentrations of the reacting substances
  • law of segregation - noun members of a pair of homologous chromosomes separate during the formation of gametes and are distributed to different gametes so that every gamete receives only one member of the pair
  • lens - noun a transparent optical device used to converge or diverge transmitted light and to form images; electronic equipment that uses a magnetic or electric field in order to focus a beam of electrons;biconvex transparent body situated behind the iris in the eye; it focuses light waves on the retina; (metaphor) a channel through which something can be seen or understood; genus of small erect or climbing herbs with pinnate leaves and small inconspicuous white flowers and small flattened pods: lentils
  • lenticel - noun one of many raised pores on the stems of woody plants that allow the interchange of gas between the atmosphere and the interior tissue
  • lichen - noun any thallophytic plant of the division Lichenes; occur as crusty patches or bushy growths on tree trunks or rocks or bare ground etc.; any of several eruptive skin diseases characterized by hard thick lesions grouped together and resembling lichens growing on rocks
  • life cycle - noun a series of stages through which an organism passes between recurrences of a primary stage; the course of developmental changes in an organism from fertilized zygote to maturity when another zygote can be produced
  • life history - noun the general progression of your working or professional life; an account of the series of events making up a person's life
  • life science - noun any of the branches of natural science dealing with the structure and behavior of living organisms
  • ligand - noun an atom or molecule or radical or ion that forms a complex around a central atom
  • light microscope - noun microscope consisting of an optical instrument that magnifies the image of an object
  • lipase - noun an enzyme secreted in the digestive tract that catalyzes the breakdown of fats into individual fatty acids that can be absorbed into the bloodstream
  • lipid - noun an oily organic compound insoluble in water but soluble in organic solvents; essential structural component of living cells (along with proteins and carbohydrates)
  • litmus - noun a coloring material (obtained from lichens) that turns red in acid solutions and blue in alkaline solutions; used as a very rough acid-base indicator
  • litmus paper - noun unsized paper treated with litmus for use as an acid-base indicator
  • liver - adj. having a reddish-brown color; noun large and complicated reddish-brown glandular organ located in the upper right portion of the abdominal cavity; secretes bile and functions in metabolism of protein and carbohydrate and fat; synthesizes substances involved in the clotting of the blood; synthesizes vitamin A; detoxifies poisonous substances and breaks down worn-out erythrocytes; liver of an animal used as meat; someone who lives in a place; a person who has a special life style
  • loam - noun a rich soil consisting of a mixture of sand and clay and decaying organic materials
  • lobe - noun a rounded projection that is part of a larger structure;(anatomy) a somewhat rounded subdivision of a bodily organ or part; the enhanced response of an antenna in a given direction as indicated by a loop in its radiation pattern; (botany) a part into which a leaf is divided
  • locus - noun the set of all points or lines that satisfy or are determined by specific conditions; the specific site of a particular gene on its chromosome; the scene of any event or action (especially the place of a meeting)
  • long bone - noun in limbs of vertebrate animals: a long cylindrical bone that contains marrow
  • loose - adj. not bound or fastened or gathered together; not compact or dense in structure or arrangement; (of a ball in sport) not in the possession or control of any player; not restrained or confined or attached; freely producing mucus; not tight; not closely constrained or constricted or constricting; not carefully arranged in a package; not fixed firmly or tightly; (of textures) full of small openings or gaps; not tense or taut; not affixed; casual and unrestrained in sexual behavior; emptying easily or excessively; not literal; having escaped, especially from confinement; not officially recognized or controlled; lacking a sense of restraint or responsibility; adv. without restraint; verb become loose or looser or less tight; make loose or looser; turn loose or free from restraint;grant freedom to; free from confinement
  • areolar - adj. relating to or like or divided into areolae
  • connective - adj. connecting or tending to connect; noun an instrumentality that connects; an uninflected function word that serves to conjoin words or phrases or clauses or sentences
  • tissue - noun part of an organism consisting of an aggregate of cells having a similar structure and function; a soft thin (usually translucent) paper; verb create a piece of cloth by interlacing strands of fabric, such as wool or cotton
  • luteinizing hormone - noun a gonadotropic hormone that is secreted by the anterior pituitary; stimulates ovulation in female mammals and stimulates androgen release in male mammals
  • LH - noun a gonadotropic hormone that is secreted by the anterior pituitary; stimulates ovulation in female mammals and stimulates androgen release in male mammals
  • Lymph - noun a thin coagulable fluid (similar to plasma but) containing white blood cells (lymphocytes) and chyle; is conveyed to the blood stream by lymphatic vessels
  • lymph - noun a thin coagulable fluid (similar to plasma but) containing white blood cells (lymphocytes) and chyle; is conveyed to the blood stream by lymphatic vessels
  • lymph node - noun the source of lymph and lymphocytes
  • lymphocyte - noun an agranulocytic leukocyte that normally makes up a quarter of the white blood cell count but increases in the presence of infection
  • lysis - noun (biochemistry) dissolution or destruction of cells such as blood cells or bacteria; recuperation in which the symptoms of an acute disease gradually subside
  • lysosome - noun an organelle found in the cytoplasm of most cells (especially in leukocytes and liver and kidney cells)
  • M - noun the 13th letter of the Roman alphabet; concentration measured by the number of moles of solute per liter of solution; the basic unit of length adopted under the Systeme International d'Unites (approximately 1.094 yards)
  • macroevolution - noun evolution on a large scale extending over geologic era and resulting in the formation of new taxonomic groups
  • macromolecule - noun any very large complex molecule; found only in plants and animals
  • macrophage - noun a large phagocyte; some are fixed and other circulate in the blood stream
  • I - noun the 9th letter of the Roman alphabet; a nonmetallic element belonging to the halogens; used especially in medicine and photography and in dyes; occurs naturally only in combination in small quantities (as in sea water or rocks)
  • malleus - noun the ossicle attached to the eardrum
  • mammal - noun any warm-blooded vertebrate having the skin more or less covered with hair; young are born alive except for the small subclass of monotremes and nourished with milk
  • mantle - noun (zoology) a protective layer of epidermis in mollusks or brachiopods that secretes a substance forming the shell; the cloak as a symbol of authority; the layer of the earth between the crust and the core; United States baseball player (1931-1997); a sleeveless garment like a cloak but shorter; hanging cloth used as a blind (especially for a window); shelf that projects from wall above fireplace; anything that covers; verb cover like a mantle; spread over a surface, like a mantle
  • marsupial - adj. of or relating to the marsupials; noun mammals of which the females have a pouch (the marsupium) containing the teats where the young are fed and carried
  • mass number - noun the sum of the number of neutrons and protons in an atomic nucleus
  • mast cell - noun a large connective tissue cell that contains histamine and heparin and serotonin which are released in allergic reactions or in response to injury or inflammation
  • matrix - noun mold used in the production of phonograph records, type, or other relief surface; the formative tissue at the base of a nail; the body substance in which tissue cells are embedded; a rectangular array of elements (or entries) set out by rows and columns; an enclosure within which something originates or develops (from the Latin for womb)
  • Matter - noun (used with negation) having consequence; a vaguely specified concern; a problem; written works (especially in books or magazines); that which has mass and occupies space; some situation or event that is thought about; verb have weight; have import, carry weight
  • matter - noun (used with negation) having consequence; a vaguely specified concern; a problem; written works (especially in books or magazines); that which has mass and occupies space; some situation or event that is thought about; verb have weight; have import, carry weight
  • medulla - noun the inner part of an organ or structure in plant or animal; lower or hindmost part of the brain; continuous with spinal cord; (`bulb' is an old term for medulla oblongata); a white fatty substance that forms a medullary sheath around the axis cylinder of some nerve fibers
  • medusa - noun one of two forms that coelenterates take: is the free-swimming sexual stage in the life cycle of a coelenterate and has a gelatinous umbrella-shaped body and tentacles; (Greek mythology) a woman transformed into a Gorgon by Athena; she was slain by Perseus; any of numerous usually marine and free-swimming coelenterates that constitute the sexually reproductive forms of hydrozoans and scyphozoans
  • megaspore - noun larger of the two types of spore produced in heterosporous plants; develops in ovule into a female gametophyte
  • megasporophyll - noun in non-flowering plants, a sporophyll that bears only megasporangia
  • meiosis - noun (genetics) cell division that produces reproductive cells in sexually reproducing organisms; the nucleus divides into four nuclei each containing half the chromosome number (leading to gametes in animals and spores in plants); understatement for rhetorical effect (especially when expressing an affirmative by negating its contrary)
  • Meiosis - noun (genetics) cell division that produces reproductive cells in sexually reproducing organisms; the nucleus divides into four nuclei each containing half the chromosome number (leading to gametes in animals and spores in plants); understatement for rhetorical effect (especially when expressing an affirmative by negating its contrary)
  • Meissner - noun German physicist (1882-1974); German anatomist (1829-1905)
  • Meissner - noun German physicist (1882-1974); German anatomist (1829-1905)
  • meninges - noun a membrane (one of 3) that envelops the brain and spinal cord
  • menopause - noun the time in a woman's life in which the menstrual cycle ends
  • menstrual cycle - noun a recurring cycle (beginning at menarche and ending at menopause) in which the endometrial lining of the uterus prepares for pregnancy; if pregnancy does not occur the lining is shed at menstruation
  • meristem - noun undifferentiated tissue from which new cells are formed, as at the tip of a stem or root
  • mesocarp - noun the middle layer of a pericarp
  • messenger RNA - noun the template for protein synthesis; the form of RNA that carries information from DNA in the nucleus to the ribosome sites of protein synthesis in the cell
  • mRNA - noun the template for protein synthesis; the form of RNA that carries information from DNA in the nucleus to the ribosome sites of protein synthesis in the cell
  • metabolism - noun the organic processes (in a cell or organism) that are necessary for life; the marked and rapid transformation of a larva into an adult that occurs in some animals
  • metacarpus - noun the part of the hand between the carpus and phalanges
  • Metaphase - noun the second stage of mitosis; the second stage of meiosis
  • metaphase - noun the second stage of mitosis; the second stage of meiosis
  • metatarsal - adj. of or relating to the metatarsus; noun any bone of the foot between the ankle and the toes
  • Metazoa - noun multicellular animals having cells differentiated into tissues and organs and usually a digestive cavity and nervous system
  • Microbiology - noun the branch of biology that studies microorganisms and their effects on humans
  • microbiology - noun the branch of biology that studies microorganisms and their effects on humans
  • microcosm - noun a miniature model of something
  • microevolution - noun evolution resulting from small specific genetic changes that can lead to a new subspecies
  • Microglia - noun neuroglial tissue of mesodermal origin that can become phagocytic
  • microglia - noun neuroglial tissue of mesodermal origin that can become phagocytic
  • micronutrient - noun a substance needed only in small amounts for normal body function (e.g., vitamins or minerals)
  • micropyle - noun minute opening in the wall of an ovule through which the pollen tube enters
  • microsporophyll - noun in non-flowering plants, a sporophyll that bears only microsporangia
  • middle ear - noun the main cavity of the ear; between the eardrum and the inner ear
  • Migration - noun the movement of persons from one country or locality to another; the periodic passage of groups of animals (especially birds or fishes) from one region to another for feeding or breeding; (chemistry) the nonrandom movement of an atom or radical from one place to another within a molecule; a group of people migrating together (especially in some given time period)
  • migration - noun the movement of persons from one country or locality to another; the periodic passage of groups of animals (especially birds or fishes) from one region to another for feeding or breeding; (chemistry) the nonrandom movement of an atom or radical from one place to another within a molecule; a group of people migrating together (especially in some given time period)
  • mineral - adj. of or containing or derived from minerals; composed of matter other than plant or animal; relating to minerals; noun solid homogeneous inorganic substances occurring in nature having a definite chemical composition
  • mineralocorticoid - noun hormone that is one of the steroids of the adrenal cortex that influences the metabolism of sodium and potassium
  • molality - noun concentration measured by the number of moles of solute per kilogram of solvent
  • molarity - noun concentration measured by the number of moles of solute per liter of solution
  • mold - noun container into which liquid is poured to create a given shape when it hardens; sculpture produced by molding; a fungus that produces a superficial growth on various kinds of damp or decaying organic matter; loose soil rich in organic matter; the process of becoming mildewed; the distinctive form in which a thing is made; verb become moldy; spoil due to humidity; fit tightly, follow the contours of; shape or influence; give direction to; make something, usually for a specific function; form by pouring (e.g., wax or hot metal) into a cast or mold; form in clay, wax, etc
  • mole - noun small velvety-furred burrowing mammal having small eyes and fossorial forefeet; a small congenital pigmented spot on the skin; spicy sauce often containing chocolate; a protective structure of stone or concrete; extends from shore into the water to prevent a beach from washing away; a spy who works against enemy espionage; the molecular weight of a substance expressed in grams; the basic unit of amount of substance adopted under the Systeme International d'Unites
  • molecular biology - noun the branch of biology that studies the structure and activity of macromolecules essential to life (and especially with their genetic role)
  • molecule - noun (physics and chemistry) the simplest structural unit of an element or compound; (nontechnical usage) a tiny piece of anything
  • Mollusca - noun gastropods; bivalves; cephalopods; chitons
  • molting - noun periodic shedding of the cuticle in arthropods or the outer skin in reptiles
  • monocarpic - adj. dying after bearing fruit only once
  • monocot - noun a monocotyledonous flowering plant; the stem grows by deposits on its inside
  • monocyte - noun a type of granular leukocyte that functions in the ingestion of bacteria
  • monoecious - adj. having male and female reproductive organs in the same plant or animal
  • monogamous - adj. (used of relationships and of individuals) having one mate
  • monogamy - noun having only one spouse at a time
  • monohybrid - noun a hybrid produced by crossing parents that are homozygous except for a single gene locus that has two alleles (as in Mendel's experiments with garden peas)
  • monomer - noun a simple compound whose molecules can join together to form polymers
  • monosaccharide - noun a sugar (like sucrose or fructose) that does not hydrolyse to give other sugars; the simplest group of carbohydrates
  • monosomy - noun chromosomal abnormality consisting of the absence of one chromosome from the normal diploid number
  • monotreme - noun the most primitive mammals comprising the only extant members of the subclass Prototheria
  • morning sickness - noun nausea early in the day; a characteristic symptom in the early months of pregnancy
  • mortality rate - noun the ratio of deaths in an area to the population of that area; expressed per 1000 per year
  • motor end plate - noun the flattened end of a motor neuron that transmits neural impulses to a muscle
  • mucin - noun a nitrogenous substance found in mucous secretions; a lubricant that protects body surfaces
  • Multiple fruit - noun fruit consisting of many individual small fruits or drupes derived from separate ovaries within a common receptacle: e.g. blackberry; raspberry; pineapple
  • multiple fruit - noun fruit consisting of many individual small fruits or drupes derived from separate ovaries within a common receptacle: e.g. blackberry; raspberry; pineapple
  • mutation - noun a change or alteration in form or qualities;(genetics) any event that changes genetic structure; any alteration in the inherited nucleic acid sequence of the genotype of an organism;(biology) an organism that has characteristics resulting from chromosomal alteration
  • Mutualism - noun the relation between two different species of organisms that are interdependent; each gains benefits from the other
  • mutualism - noun the relation between two different species of organisms that are interdependent; each gains benefits from the other
  • mycelium - noun the vegetative part of a fungus consisting of a mass of branching threadlike hyphae
  • mycology - noun the branch of botany that studies fungi and fungus-caused diseases
  • mycosis - noun an inflammatory condition caused by a fungus
  • myelin - noun a white fatty substance that forms a medullary sheath around the axis cylinder of some nerve fibers
  • myocardial infarction - noun destruction of heart tissue resulting from obstruction of the blood supply to the heart muscle
  • myocardium - noun the middle muscular layer of the heart wall
  • myofibril - noun one of many contractile filaments that make up a striated muscle fiber
  • Myopia - noun (ophthalmology) eyesight abnormality resulting from the eye's faulty refractive ability; distant objects appear blurred
  • myopia - noun (ophthalmology) eyesight abnormality resulting from the eye's faulty refractive ability; distant objects appear blurred
  • myosin - noun the commonest protein in muscle; a globulin that combines with actin to form actomyosin
  • N - noun the 14th letter of the Roman alphabet; (of a solution) concentration expressed in gram equivalents of solute per liter; a unit of force equal to the force that imparts an acceleration of 1 m/sec/sec to a mass of 1 kilogram; equal to 100,000 dynes; the cardinal compass point that is at 0 or 360 degrees; a common nonmetallic element that is normally a colorless odorless tasteless inert diatomic gas; constitutes 78 percent of the atmosphere by volume; a constituent of all living tissues
  • nacre - noun the iridescent internal layer of a mollusk shell
  • nasal cavity - noun either of the two cavities lying between the floor of the cranium and the roof of the mouth and extending from the face to the pharynx
  • cell - noun (biology) the basic structural and functional unit of all organisms; they may exist as independent units of life (as in monads) or may form colonies or tissues as in higher plants and animals; a device that delivers an electric current as the result of a chemical reaction; a room where a prisoner is kept; small room is which a monk or nun lives; any small compartment; a small unit serving as part of or as the nucleus of a larger political movement; a hand-held mobile radiotelephone for use in an area divided into small sections, each with its own short-range transmitter/receiver
  • natural science - noun the sciences involved in the study of the physical world and its phenomena
  • Natural selection - noun a natural process resulting in the evolution of organisms best adapted to the environment
  • natural selection - noun a natural process resulting in the evolution of organisms best adapted to the environment
  • nectar - noun fruit juice especially when undiluted; a sweet liquid secretion that is attractive to pollinators; (classical mythology) the food and drink of the gods; mortals who ate it became immortal
  • Nematoda - noun unsegmented worms: roundworms; threadworms; eelworms
  • nephron - noun any of the small tubules that are the excretory units of the vertebrate kidney
  • neritic zone - noun the ocean waters from the low tide mark to a depth of about 100 fathoms
  • neural tube - noun a tube of ectodermal tissue in the embryo from which the brain and spinal cord develop
  • neurobiology - noun the branch of biology that deals with the anatomy and physiology and pathology of the nervous system
  • neutron - noun an elementary particle with 0 charge and mass about equal to a proton; enters into the structure of the atomic nucleus
  • neutrophil - noun the chief phagocytic leukocyte; stains with either basic or acid dyes
  • node - noun (computer science) any computer that is hooked up to a computer network; any bulge or swelling of an anatomical structure or part; (astronomy) a point where an orbit crosses a plane; (physics) the point of minimum displacement in a periodic system; any thickened enlargement; a connecting point at which several lines come together; the source of lymph and lymphocytes
  • nodule - noun a small node; (mineralogy) a small rounded lump of mineral substance (usually harder than the surrounding rock or sediment); small rounded wartlike protuberance on a plant
  • noncellular - adj. not made up of or divided into cells
  • nondisjunction - noun meiosis in which there is a failure of paired homologous chromosomes to separate; results in an abnormal number of chromosomes in the daughter cells
  • type - noun a small metal block bearing a raised character on one end; produces a printed character when inked and pressed on paper; a subdivision of a particular kind of thing; all of the tokens of the same symbol; printed characters; (biology) the taxonomic group whose characteristics are used to define the next higher taxon; a person of a specified kind (usually with many eccentricities); verbidentify as belonging to a certain type; write by means of a keyboard with types
  • norepinephrine - noun a catecholamine precursor of epinephrine that is secreted by the adrenal medulla and also released at synapses
  • notochord - noun a flexible rodlike structure that forms the supporting axis of the body in the lowest chordates and lowest vertebrates and in embryos of higher vertebrates
  • nucleic acid - noun (biochemistry) any of various macromolecules composed of nucleotide chains that are vital constituents of all living cells
  • nucleolus - noun a small round body of protein in a cell nucleus; such organelles contain RNA and are involved in protein synthesis
  • nucleoplasm - noun the protoplasm that constitutes the nucleus of a cell
  • nucleotide - noun a phosphoric ester of a nucleoside; the basic structural unit of nucleic acids (DNA or RNA)
  • nucleus - noun a part of the cell containing DNA and RNA and responsible for growth and reproduction; any histologically identifiable mass of neural cell bodies in the brain or spinal cord; the positively charged dense center of an atom; (astronomy) the center of the head of a comet; consists of small solid particles of ice and frozen gas that vaporizes on approaching the sun to form the coma and tail; a small group of indispensable persons or things
  • nutrient - adj. of or providing nourishment; noun any substance that can be metabolized by an organism to give energy and build tissue
  • O - noun the blood group whose red cells carry neither the A nor B antigens; the 15th letter of the Roman alphabet; a nonmetallic bivalent element that is normally a colorless odorless tasteless nonflammable diatomic gas; constitutes 21 percent of the atmosphere by volume; the most abundant element in the earth's crust
  • occipital - adj. of or relating to the occiput
  • occipital lobe - noun that part of the cerebral cortex in either hemisphere of the brain lying in the back of the head
  • olfaction - noun the faculty that enables us to distinguish scents
  • olfactory bulb - noun one of two enlargements at the terminus of the olfactory nerve at the base of the brain just above the nasal cavities
  • Omega - noun the last (24th) letter of the Greek alphabet; the ending of a series or sequence
  • omnivore - noun an animal that feeds on both animal and vegetable substances; a person who eats all kinds of foods
  • oncogene - noun a gene that causes normal cells to change into cancerous tumor cells
  • operant conditioning - noun conditioning in which an operant response is brought under stimulus control by virtue of presenting reinforcement contingent upon the occurrence of the operant response
  • operator - noun an agent that operates some apparatus or machine; someone who owns or operates a business; a speculator who trades aggressively on stock or commodity markets;(mathematics) a symbol that represents a function from functions to functions; a shrewd or unscrupulous person who knows how to circumvent difficulties
  • operculum - noun a hard flap serving as a cover for (a) the gill slits in fishes or (b) the opening of the shell in certain gastropods when the body is retracted
  • operon - noun a segment of DNA containing adjacent genes including structural genes and an operator gene and a regulatory gene
  • Opposition - noun a body of people united in opposing something;the major political party opposed to the party in office and prepared to replace it if elected; a contestant that you are matched against; a direction opposite to another; the relation between opposed entities;the action of opposing something that you disapprove or disagree with; the act of hostile groups opposing each other; an armed adversary (especially a member of an opposing military force)
  • opposition - noun a body of people united in opposing something;the major political party opposed to the party in office and prepared to replace it if elected; a contestant that you are matched against; a direction opposite to another; the relation between opposed entities;the action of opposing something that you disapprove or disagree with; the act of hostile groups opposing each other; an armed adversary (especially a member of an opposing military force)
  • opsonization - noun process whereby opsonins make an invading microorganism more susceptible to phagocytosis
  • orbital - adj. of or relating to the eye socket; of or relating to an orbit
  • order - noun the act of putting things in a sequential arrangement;(architecture) one of original three styles of Greek architecture distinguished by the type of column and entablature used or a style developed from the original three by the Romans; a degree in a continuum of size or quantity; a commercial document used to request someone to supply something in return for payment and providing specifications and quantities; a body of rules followed by an assembly; (often plural) a command given by a superior (e.g., a military or law enforcement officer) that must be obeyed; a request for food or refreshment (as served in a restaurant or bar etc.);(biology) taxonomic group containing one or more families; a group of person living under a religious rule; established customary state (especially of society); a legally binding command or decision entered on the court record (as if issued by a court or judge); a formal association of people with similar interests; logical or comprehensible arrangement of separate elements; (usually plural) the status or rank or office of a Christian clergyman in an ecclesiastical hierarchy; a condition of regular or proper arrangement; verb place in a certain order; bring order to or into;make a request for something; give instructions to or direct somebody to do something with authority; issue commands or orders for; assign a rank or rating to; arrange thoughts, ideas, temporal events; appoint to a clerical posts; bring into conformity with rules or principles or usage; impose regulations
  • organelle - noun a specialized part of a cell; analogous to an organ
  • organism - noun a living thing that has (or can develop) the ability to act or function independently; a system considered analogous in structure or function to a living body
  • Organs - noun edible viscera of a butchered animal
  • origin - noun properties attributable to your ancestry; the point of intersection of coordinate axes; where the values of the coordinates are all zero; an event that is a beginning; a first part or stage of subsequent events; the descendants of one individual; the place where something begins, where it springs into being
  • osmoreceptor - noun sensory end organ that responds to changes in osmotic pressure
  • Osmosis - noun diffusion of molecules through a semipermeable membrane from a place of higher concentration to a place of lower concentration until the concentration on both sides is equal
  • osmosis - noun diffusion of molecules through a semipermeable membrane from a place of higher concentration to a place of lower concentration until the concentration on both sides is equal
  • osmotic pressure - noun (physical chemistry) the pressure exerted by a solution necessary to prevent osmosis into that solution when it is separated from the pure solvent by a semipermeable membrane
  • osseous tissue - noun the porous calcified substance from which bones are made
  • ossicle - noun a small bone; especially one in the middle ear
  • Ossification - noun hardened conventionality; the developmental process of bone formation; the process of becoming rigidly fixed in a conventional pattern of thought or behavior; the calcification of soft tissue into a bonelike material
  • ossification - noun hardened conventionality; the developmental process of bone formation; the process of becoming rigidly fixed in a conventional pattern of thought or behavior; the calcification of soft tissue into a bonelike material
  • Osteichthyes - noun a class of fish having a skeleton composed of bone in addition to cartilage
  • osteoclast - noun cell that functions in the breakdown and resorption of bone tissue
  • ostracoderm - noun extinct fishlike jawless vertebrate having a heavily armored body; of the Paleozoic
  • outer ear - noun the part of the ear visible externally
  • oval window - noun fenestra that has the base of the stapes attached to it
  • ovary - noun (vertebrates) one of usually two organs that produce ova and secrete estrogen and progesterone; the organ that bears the ovules of a flower
  • oviduct - noun either of a pair of tubes conducting the egg from the ovary to the uterus
  • ovulation - noun the expulsion of an ovum from the ovary (usually midway in the menstrual cycle)
  • ovule - noun a small or immature ovum; a small body that contains the female germ cell of a plant; develops into a seed after fertilization
  • oxygen - noun a nonmetallic bivalent element that is normally a colorless odorless tasteless nonflammable diatomic gas; constitutes 21 percent of the atmosphere by volume; the most abundant element in the earth's crust
  • oxytocin - noun hormone secreted by the posterior pituitary gland (trade name Pitocin); stimulates contractions of the uterus and ejection of milk
  • P - noun the 16th letter of the Roman alphabet; a multivalent nonmetallic element of the nitrogen family that occurs commonly in inorganic phosphate rocks and as organic phosphates in all living cells; is highly reactive and occurs in several allotropic forms
  • P - noun the 16th letter of the Roman alphabet; a multivalent nonmetallic element of the nitrogen family that occurs commonly in inorganic phosphate rocks and as organic phosphates in all living cells; is highly reactive and occurs in several allotropic forms
  • p - noun the 16th letter of the Roman alphabet; a multivalent nonmetallic element of the nitrogen family that occurs commonly in inorganic phosphate rocks and as organic phosphates in all living cells; is highly reactive and occurs in several allotropic forms
  • p - noun the 16th letter of the Roman alphabet; a multivalent nonmetallic element of the nitrogen family that occurs commonly in inorganic phosphate rocks and as organic phosphates in all living cells; is highly reactive and occurs in several allotropic forms
  • P - noun the 16th letter of the Roman alphabet; a multivalent nonmetallic element of the nitrogen family that occurs commonly in inorganic phosphate rocks and as organic phosphates in all living cells; is highly reactive and occurs in several allotropic forms
  • P - noun the 16th letter of the Roman alphabet; a multivalent nonmetallic element of the nitrogen family that occurs commonly in inorganic phosphate rocks and as organic phosphates in all living cells; is highly reactive and occurs in several allotropic forms
  • Pacinian corpuscle - noun a specialized bulblike nerve ending located in the subcutaneous tissue of the skin; occurs abundantly in the skin of palms and soles and joints and genitals
  • packing - noun carrying something in a pack on the back; the enclosure of something in a package or box; any material used especially to protect something
  • Paleontology - noun the earth science that studies fossil organisms and related remains
  • paleontology - noun the earth science that studies fossil organisms and related remains
  • Pan - noun chimpanzees; more closely related to Australopithecus than to other pongids; shallow container made of metal; cooking utensil consisting of a wide metal vessel; (Greek mythology) god of fields and woods and shepherds and flocks; represented as a man with goat's legs and horns and ears; identified with Roman Sylvanus or Faunus; verb express a totally negative opinion of; wash dirt in a pan to separate out the precious minerals; make a sweeping movement
  • pancreas - noun a large elongated exocrine gland located behind the stomach; secretes pancreatic juice and insulin
  • pandemic - adj. existing everywhere; epidemic over a wide geographical area; noun an epidemic that is geographically widespread; occurring throughout a region or even throughout the world
  • Pangaea - noun (plate tectonics) a hypothetical continent including all the landmass of the earth prior to the Triassic period when it split into Laurasia and Gondwanaland
  • papilla - noun a small projection of tissue at the base of a hair or tooth or feather; a small nipple-shaped protuberance concerned with taste, touch, or smell; (botany) a tiny outgrowth on the surface of a petal or leaf
  • parapodium - noun one of a pair of fleshy appendages of a polychete annelid that functions in locomotion and breathing
  • parasite - noun an animal or plant that lives in or on a host (another animal or plant); it obtains nourishment from the host without benefiting or killing the host; a follower who hangs around a host (without benefit to the host) in hope of gain or advantage
  • parasitic plant - noun plant living on another plant and obtaining organic nutriment from it
  • Parasitism - noun the relation between two different kinds of organisms in which one receives benefits from the other by causing damage to it (usually not fatal damage)
  • parasitism - noun the relation between two different kinds of organisms in which one receives benefits from the other by causing damage to it (usually not fatal damage)
  • system - noun instrumentality that combines interrelated interacting artifacts designed to work as a coherent entity; the living body considered as made up of interdependent components forming a unified whole; a group of physiologically or anatomically related organs or parts; a complex of methods or rules governing behavior;a procedure or process for obtaining an objective; a group of independent but interrelated elements comprising a unified whole;(physical chemistry) a sample of matter in which substances in different phases are in equilibrium; an ordered manner; orderliness by virtue of being methodical and well organized; an organized structure for arranging or classifying
  • parathyroid gland - noun any one of four endocrine glands situated above or within the thyroid gland
  • parathyroid hormone - noun hormone synthesized and released into the blood stream by the parathyroid glands; regulates phosphorus and calcium in the body and functions in neuromuscular excitation and blood clotting
  • Parazoa - noun multicellular organisms having less-specialized cells than in the Metazoa; comprises the single phylum Porifera
  • parietal - adj. of or relating to or associated with the parietal bones in the cranium
  • parietal lobe - noun that part of the cerebral cortex in either hemisphere of the brain lying below the crown of the head
  • Parkinson - noun British historian noted for ridicule of bureaucracies (1909-1993); English surgeon (1755-1824)
  • Parthenogenesis - noun process in which an unfertilized egg develops into a new individual; common among insects and some other arthropods; human conception without fertilization by a man
  • parthenogenesis - noun process in which an unfertilized egg develops into a new individual; common among insects and some other arthropods; human conception without fertilization by a man
  • particulate matter - noun a small discrete mass of solid or liquid matter that remains individually dispersed in gas or liquid emissions (usually considered to be an atmospheric pollutant)
  • passive immunity - noun an impermanent form of acquired immunity in which antibodies against a disease are acquired naturally (as through the placenta to an unborn child) or artificially (as by injection of antiserum)
  • Passive transport - noun transport of a substance across a cell membrane by diffusion; expenditure of energy is not required
  • passive transport - noun transport of a substance across a cell membrane by diffusion; expenditure of energy is not required
  • patella - noun type genus of the family Patellidae: common European limpets; a small flat triangular bone in front of the knee that protects the knee joint
  • pathogen - noun any disease-producing agent (especially a virus or bacterium or other microorganism)
  • pattern - noun a model considered worthy of imitation; a customary way of operation or behavior; a decorative or artistic work;something regarded as a normative example; something intended as a guide for making something else; a perceptual structure;graphical representation (in polar or Cartesian coordinates) of the spatial distribution of radiation from an antenna as a function of angle; the path that is prescribed for an airplane that is preparing to land at an airport; verb form a pattern; plan or create according to a model or models
  • peat moss - noun any of various pale or ashy mosses of the genus Sphagnum whose decomposed remains form peat
  • pectoral girdle - noun a skeletal support to which the forelimbs of vertebrates are attached
  • pellicle - noun thin protective membrane in some protozoa
  • pelvic girdle - noun the structure of the vertebrate skeleton supporting the lower limbs in humans and the hind limbs or corresponding parts in other vertebrates
  • penis - noun the male organ of copulation (`member' is a euphemism)
  • Pepsin - noun an enzyme produced in the stomach that splits proteins into peptones
  • pepsin - noun an enzyme produced in the stomach that splits proteins into peptones
  • pepsinogen - noun precursor of pepsin; stored in the stomach walls and converted to pepsin by hydrochloric acid in the stomach
  • peptide bond - noun the primary linkage of all protein structures; the chemical bond between the carboxyl groups and amino groups that unites a peptide
  • Perception - noun the process of perceiving; knowledge gained by perceiving; a way of conceiving something; becoming aware of something via the senses; the representation of what is perceived; basic component in the formation of a concept
  • perception - noun the process of perceiving; knowledge gained by perceiving; a way of conceiving something; becoming aware of something via the senses; the representation of what is perceived; basic component in the formation of a concept
  • perianth - noun collective term for the outer parts of a flower consisting of the calyx and corolla and enclosing the stamens and pistils
  • pericardium - noun a serous membrane with two layers that surrounds the heart
  • pericarp - noun the ripened and variously modified walls of a plant ovary
  • periodic table - noun a tabular arrangement of the chemical elements according to atomic number as based on the periodic law
  • peristalsis - noun the process of wavelike muscle contractions of the alimentary tract that moves food along
  • peristome - noun region around the mouth in various invertebrates;(botany) fringe of toothlike appendages surrounding the mouth of a moss capsule
  • permissive - adj. granting or inclined or able to grant permission; not strict in discipline; not preventive
  • petal - noun part of the perianth that is usually brightly colored
  • petiole - noun the slender stem that supports the blade of a leaf
  • pH scale - noun (from potential of Hydrogen) the logarithm of the reciprocal of hydrogen-ion concentration in gram atoms per liter; provides a measure on a scale from 0 to 14 of the acidity or alkalinity of a solution (where 7 is neutral and greater than 7 is more basic and less than 7 is more acidic)
  • pharynx - noun the passage to the stomach and lungs; in the front part of the neck below the chin and above the collarbone
  • phenotype - noun what an organism looks like as a consequence of the interaction of its genotype and the environment
  • pheromone - noun a chemical substance secreted externally by some animals (especially insects) that influences the physiology or behavior of other animals of the same species
  • Phloem - noun (botany) tissue that conducts synthesized food substances (e.g., from leaves) to parts where needed; consists primarily of sieve tubes
  • phloem - noun (botany) tissue that conducts synthesized food substances (e.g., from leaves) to parts where needed; consists primarily of sieve tubes
  • phosphatase - noun any of a group of enzymes that act as a catalyst in the hydrolysis of organic phosphates
  • phospholipid - noun any of various compounds composed of fatty acids and phosphoric acid and a nitrogenous base; an important constituent of membranes
  • photon - noun a quantum of electromagnetic radiation; an elementary particle that is its own antiparticle
  • phylogeny - noun (biology) the sequence of events involved in the evolutionary development of a species or taxonomic group of organisms
  • phylum - noun (biology) the major taxonomic group of animals and plants; contains classes; (linguistics) a large group of languages that are historically related
  • Phytoplankton - noun photosynthetic or plant constituent of plankton; mainly unicellular algae
  • pia mater - noun the highly vascular innermost of the 3 meninges
  • pigment - noun dry coloring matter (especially a powder to be mixed with a liquid to produce paint etc); verb color or dye with a pigment;acquire pigment; become colored or imbued
  • pilus - noun hairlike structure especially on the surface of a cell or microorganism; any of the cylindrical filaments characteristically growing from the epidermis of a mammal
  • pinna - noun division of a usually pinnately divided leaf; the externally visible cartilaginous structure of the external ear
  • pistil - noun the female ovule-bearing part of a flower composed of ovary and style and stigma
  • pith - noun soft spongelike central cylinder of the stems of most flowering plants; the choicest or most essential or most vital part of some idea or experience; verb remove the pith from (a plant)
  • pituitary gland - noun the master gland of the endocrine system; located at the base of the brain
  • pivot joint - noun a freely moving joint in which movement is limited to rotation
  • placenta - noun the vascular structure in the uterus of most mammals providing oxygen and nutrients for and transferring wastes from the developing fetus; that part of the ovary of a flowering plant where the ovules form
  • plagiarism - noun the act of plagiarizing; taking someone's words or ideas as if they were your own; a piece of writing that has been copied from someone else and is presented as being your own work
  • plankton - noun the aggregate of small plant and animal organisms that float or drift in great numbers in fresh or salt water
  • plasma - noun colorless watery fluid of blood and lymph containing no cells and in which erythrocytes and leukocytes and platelets are suspended; (physical chemistry) a fourth state of matter distinct from solid or liquid or gas and present in stars and fusion reactors; a gas becomes a plasma when it is heated until the atoms lose all their electrons, leaving a highly electrified collection of nuclei and free electrons; a green slightly translucent variety of chalcedony used as a gemstone
  • plasma cell - noun a cell that develops from a B lymphocyte in reaction to a specific antigen; found in bone marrow and sometimes in the blood
  • plasma membrane - noun a thin membrane (a double layer of lipids) enclosing the cytoplasm of a cell; proteins in the membrane control passage of ions (like sodium or potassium or calcium) in and out of the cell
  • plasmid - noun a small cellular inclusion consisting of a ring of DNA that is not in a chromosome but is capable of autonomous replication
  • plastid - noun any of various small particles in the cytoplasm of the cells of plants and some animals containing pigments or starch or oil or protein
  • plastron - noun (zoology) the part of a turtle's shell forming its underside; a large pad worn by a fencer to protect the chest; a metal breastplate that was worn under a coat of mail; the front of man's dress shirt; the ornamental front of a woman's bodice or shirt
  • platelet - noun tiny bits of protoplasm found in vertebrate blood; essential for blood clotting
  • Platyrrhini - noun New World monkeys: capuchin; douroucouli; howler monkey; saki; spider monkey; squirrel monkey; titi; uakari; woolly monkey; marmoset; tamarin
  • pleura - noun the thin serous membrane around the lungs and inner walls of the chest
  • Pleurisy - noun inflammation of the pleura of the lungs (especially the parietal layer)
  • pleurisy - noun inflammation of the pleura of the lungs (especially the parietal layer)
  • plumule - noun down feather of young birds; persists in some adult birds
  • point mutation - noun a mutation due to an intramolecular reorganization of a gene
  • pollen tube - noun (botany) a slender tubular outgrowth from a pollen grain when deposited on the stigma for a flower; it penetrates the style and conveys the male gametes to the ovule
  • pollination - noun transfer of pollen from the anther to the stigma of a plant
  • polyandrous - adj. having more than one husband at a time
  • polyandry - noun having more than one husband at a time
  • polygenic - adj. of or relating to an inheritable character that is controlled by several genes at once; of or related to or determined by polygenes
  • Polygynous - adj. having more than one wife at a time
  • polygyny - noun having more than one wife at a time
  • polymer - noun a naturally occurring or synthetic compound consisting of large molecules made up of a linked series of repeated simple monomers
  • polymorphic - adj. having or occurring in several distinct forms;relating to the occurrence of more than one kind of individual (independent of sexual differences) in an interbreeding population;relating to the crystallization of a compound in two or more different forms
  • polyp - noun one of two forms that coelenterates take e.g. a hydra or coral: usually sedentary and has a hollow cylindrical body usually with a ring of tentacles around the mouth; a small vascular growth on the surface of a mucous membrane
  • polypeptide - noun a peptide containing 10 to more than 100 amino acids
  • polyploid - adj. of a cell or organism having more than twice the haploid number of chromosomes; noun (genetics) an organism or cell having more than twice the haploid number of chromosomes
  • polysaccharide - noun any of a class of carbohydrates whose molecules contain chains of monosaccharide molecules
  • Pongo - noun type genus of the family Pongidae: orangutans
  • population - noun the act of populating (causing to live in a place);(statistics) the entire aggregation of items from which samples can be drawn; a group of organisms of the same species populating a given area; the people who inhabit a territory or state; the number of inhabitants (either the total number or the number of a particular race or class) in a given place (country or city etc.)
  • N - noun the 14th letter of the Roman alphabet; (of a solution) concentration expressed in gram equivalents of solute per liter; a unit of force equal to the force that imparts an acceleration of 1 m/sec/sec to a mass of 1 kilogram; equal to 100,000 dynes; the cardinal compass point that is at 0 or 360 degrees; a common nonmetallic element that is normally a colorless odorless tasteless inert diatomic gas; constitutes 78 percent of the atmosphere by volume; a constituent of all living tissues
  • Porifera - noun coextensive with the subkingdom Parazoa: sponges
  • posterior pituitary - noun the posterior lobe of the pituitary body; primarily glandular in nature
  • potential energy - noun the mechanical energy that a body has by virtue of its position; stored energy
  • predator - noun any animal that lives by preying on other animals;someone who attacks in search of booty
  • presbyopia - noun farsightedness resulting from a reduced ability to focus caused by loss of elasticity of the crystalline lens with age
  • primary - adj. not derived from or reducible to something else; basic; of first rank or importance or value; direct and immediate rather than secondhand; of primary importance; most important element; of or being the essential or basic part; noun a preliminary election where delegates or nominees are chosen; one of the main flight feathers projecting along the outer edge of a bird's wing; coil forming the part of an electrical circuit such that changing current in it induces a current in a neighboring circuit
  • main - adj. of force; of the greatest possible intensity; (of a clause) capable of standing syntactically alone as a complete sentence;most important element; noun a principal pipe in a system that distributes water or gas or electricity or that collects sewage; any very large body of (salt) water
  • primary feather - noun one of the main flight feathers projecting along the outer edge of a bird's wing
  • Primates - noun an animal order including lemurs and tarsiers and monkeys and apes and human beings
  • primer - noun an introductory textbook; the first or preliminary coat of paint or size applied to a surface; any igniter that is used to initiate the burning of a propellant
  • prion - noun (microbiology) an infectious protein particle similar to a virus but lacking nucleic acid; thought to be the agent responsible for scrapie and other degenerative diseases of the nervous system
  • probe - noun an investigation conducted using a flexible surgical instrument to explore an injury or a body cavity; an exploratory action or expedition; a flexible slender surgical instrument used to explore wounds or body cavities; an inquiry into unfamiliar or questionable activities; verb question or examine thoroughly and closely; examine physically with or as if with a probe
  • product - noun an artifact that has been created by someone or some process; a quantity obtained by multiplication; a consequence of someone's efforts or of a particular set of circumstances; a chemical substance formed as a result of a chemical reaction;commodities offered for sale; the set of elements common to two or more sets
  • productive - adj. producing or capable of producing (especially abundantly); yielding positive results; marked by great fruitfulness;having the ability to produce or originate
  • Progesterone - noun a steroid hormone (trade name Lipo-Lutin) produced in the ovary; prepares and maintains the uterus for pregnancy
  • progesterone - noun a steroid hormone (trade name Lipo-Lutin) produced in the ovary; prepares and maintains the uterus for pregnancy
  • progymnosperm - noun an ancestral fossil type from which modern gymnosperms are thought to have derived
  • prokaryote - noun a unicellular organism having cells lacking membrane-bound nuclei; bacteria are the prime example but also included are blue-green algae and actinomycetes and mycoplasma
  • prolactin - noun gonadotropic hormone secreted by the anterior pituitary; in females it stimulates growth of the mammary glands and lactation after parturition
  • promoter - noun someone who is an active supporter and advocate;a sponsor who books and stages public entertainments
  • Pronation - noun rotation of the hands and forearms so that the palms face downward
  • pronation - noun rotation of the hands and forearms so that the palms face downward
  • Prophase - noun the first stage of mitosis; the first stage of meiosis
  • prophase - noun the first stage of mitosis; the first stage of meiosis
  • proprioception - noun the ability to sense the position and location and orientation and movement of the body and its parts
  • prosimian - noun primitive primates having large ears and eyes and characterized by nocturnal habits
  • prostate gland - noun a firm partly muscular chestnut sized gland in males at the neck of the urethra; produces a viscid secretion that is the fluid part of semen
  • protease - noun any enzyme that catalyzes the splitting of proteins into smaller peptide fractions and amino acids by a process known as proteolysis
  • protein - noun any of a large group of nitrogenous organic compounds that are essential constituents of living cells; consist of polymers of amino acids; essential in the diet of animals for growth and for repair of tissues; can be obtained from meat and eggs and milk and legumes
  • proteome - noun the full complement of proteins produced by a particular genome
  • Proteomics - noun the branch of genetics that studies the full set of proteins encoded by a genome
  • proteomics - noun the branch of genetics that studies the full set of proteins encoded by a genome
  • proto-oncogene - noun a normal gene that has the potential to become an oncogene
  • proton - noun a stable particle with positive charge equal to the negative charge of an electron
  • Protraction - noun the act of prolonging something; the consequence of being lengthened in duration
  • protraction - noun the act of prolonging something; the consequence of being lengthened in duration
  • punctuated equilibrium - noun a theory of evolution holding that evolutionary change in the fossil record came in fits and starts rather than in a steady process of slow change
  • pupil - noun contractile aperture in the iris of the eye; a young person attending school (up through senior high school); a learner who is enrolled in an educational institution
  • purine - noun a colorless crystalline organic base containing nitrogen; the parent compound of various biologically important substances; any of several bases that are derivatives of purine
  • pyrimidine - noun a heterocyclic organic compound with a penetrating odor; any of several basic compounds derived from pyrimidine
  • Q - noun the 17th letter of the Roman alphabet
  • quiescent - adj. causing no symptoms; being quiet or still or inactive; not active or activated; marked by a state of tranquil repose
  • R - noun the 18th letter of the Roman alphabet; the length of a line segment between the center and circumference of a circle or sphere; (physics) the universal constant in the gas equation: pressure times volume = R times temperature; equal to 8.3143 joules per kelvin per mole; a unit of radiation exposure; the dose of ionizing radiation that will produce 1 electrostatic unit of electricity in 1 cc of dry air
  • radicle - noun (anatomy) a small structure resembling a rootlet (such as a fibril of a nerve)
  • radioisotope - noun a radioactive isotope of an element; produced either naturally or artificially
  • radius - noun the length of a line segment between the center and circumference of a circle or sphere; the outer and slightly shorter of the two bones of the human forearm; a circular region whose area is indicated by the length of its radius; a straight line from the center to the perimeter of a circle (or from the center to the surface of a sphere); support consisting of a radial member of a wheel joining the hub to the rim
  • raphe - noun a ridge that forms a seam between two parts
  • reactant - noun a chemical substance that is present at the start of a chemical reaction
  • reception - noun the act of receiving; (American football) the act of catching a pass in football; quality or fidelity of a received broadcast;the manner in which something is greeted; a formal party of people; as after a wedding
  • receptive - adj. able to absorb liquid (not repellent); open to arguments, ideas, or change; ready or willing to receive favorably; of a nerve fiber or impulse originating outside and passing toward the central nervous system
  • receptor - noun a cellular structure that is postulated to exist in order to mediate between a chemical agent that acts on nervous tissue and the physiological response; an organ having nerve endings (in the skin or viscera or eye or ear or nose or mouth) that respond to stimulation
  • recessive - adj. (of genes) producing its characteristic phenotype only when its allele is identical; of or pertaining to a recession; nounan allele that produces its characteristic phenotype only when its paired allele is identical
  • reciprocal cross - noun hybridization involving a pair of crosses that reverse the sexes associated with each genotype
  • recombinant DNA - noun genetically engineered DNA made by recombining fragments of DNA from different organisms
  • recruitment - noun the act of getting recruits; enlisting people for the army (or for a job or a cause etc.)
  • rectum - noun the terminal section of the alimentary canal; from the sigmoid flexure to the anus
  • red blood cell - noun a mature blood cell that contains hemoglobin to carry oxygen to the bodily tissues; a biconcave disc that has no nucleus
  • reduction - noun the act of reducing complexity; any process in which electrons are added to an atom or ion (as by removing oxygen or adding hydrogen); always occurs accompanied by oxidation of the reducing agent; the act of decreasing or reducing something
  • reduction division - noun (genetics) cell division that produces reproductive cells in sexually reproducing organisms; the nucleus divides into four nuclei each containing half the chromosome number (leading to gametes in animals and spores in plants)
  • refractory period - noun (neurology) the time after a neuron fires or a muscle fiber contracts during which a stimulus will not evoke a response
  • cell - noun (biology) the basic structural and functional unit of all organisms; they may exist as independent units of life (as in monads) or may form colonies or tissues as in higher plants and animals; a device that delivers an electric current as the result of a chemical reaction; a room where a prisoner is kept; small room is which a monk or nun lives; any small compartment; a small unit serving as part of or as the nucleus of a larger political movement; a hand-held mobile radiotelephone for use in an area divided into small sections, each with its own short-range transmitter/receiver
  • reinforcement - noun information that makes more forcible or convincing; a military operation (often involving new supplies of men and materiel) to strengthen a military force or aid in the performance of its mission; an act performed to strengthen approved behavior; a device designed to provide additional strength; (psychology) a stimulus that strengthens or weakens the behavior that produced it
  • renal artery - noun an artery originating from the abdominal aorta and supplying the kidneys and adrenal glands and ureters
  • renal corpuscle - noun the capsule that contains Bowman's capsule and a glomerulus at the expanded end of a nephron
  • renal pelvis - noun a structure shaped like a funnel in the outlet of the kidney into which urine is discharged before passing into the ureter
  • renal vein - noun veins that accompany renal arteries; open into the vena cava at the level of the 2nd lumbar vertebra
  • renin - noun a proteolytic enzyme secreted by the kidneys; catalyzes the formation of angiotensin and thus affects blood pressure
  • RV - noun a motorized wheeled vehicle used for camping or other recreational activities
  • Resilience - noun the physical property of a material that can return to its original shape or position after deformation that does not exceed its elastic limit; an occurrence of rebounding or springing back
  • resilience - noun the physical property of a material that can return to its original shape or position after deformation that does not exceed its elastic limit; an occurrence of rebounding or springing back
  • ecological - adj. of or relating to the science of ecology;characterized by the interdependence of living organisms in an environment
  • resistance - noun the action of opposing something that you disapprove or disagree with; the military action of resisting the enemy's advance; group action in opposition to those in power;(psychiatry) an unwillingness to bring repressed feelings into conscious awareness; the degree of unresponsiveness of a disease-causing microorganism to antibiotics or other drugs (as in penicillin-resistant bacteria); any mechanical force that tends to retard or oppose motion; an electrical device that resists the flow of electrical current; a secret group organized to overthrow a government or occupation force; a material's opposition to the flow of electric current; measured in ohms; (medicine) the condition in which an organism can resist disease
  • Resistance - noun the action of opposing something that you disapprove or disagree with; the military action of resisting the enemy's advance; group action in opposition to those in power;(psychiatry) an unwillingness to bring repressed feelings into conscious awareness; the degree of unresponsiveness of a disease-causing microorganism to antibiotics or other drugs (as in penicillin-resistant bacteria); any mechanical force that tends to retard or oppose motion; an electrical device that resists the flow of electrical current; a secret group organized to overthrow a government or occupation force; a material's opposition to the flow of electric current; measured in ohms; (medicine) the condition in which an organism can resist disease
  • resistance - noun the action of opposing something that you disapprove or disagree with; the military action of resisting the enemy's advance; group action in opposition to those in power;(psychiatry) an unwillingness to bring repressed feelings into conscious awareness; the degree of unresponsiveness of a disease-causing microorganism to antibiotics or other drugs (as in penicillin-resistant bacteria); any mechanical force that tends to retard or oppose motion; an electrical device that resists the flow of electrical current; a secret group organized to overthrow a government or occupation force; a material's opposition to the flow of electric current; measured in ohms; (medicine) the condition in which an organism can resist disease
  • ecological - adj. of or relating to the science of ecology;characterized by the interdependence of living organisms in an environment
  • resorption - noun the organic process in which the substance of some differentiated structure that has been produced by the body undergoes lysis and assimilation
  • respiratory distress syndrome - noun an acute lung disease of the newborn (especially the premature newborn); lungs cannot expand because of a wetting agent is lacking; characterized by rapid shallow breathing and cyanosis and the formation of a glassy hyaline membrane over the alveoli
  • respiratory quotient - noun the ratio of the volume of carbon dioxide expired to the volume of oxygen consumed by an organism or cell in a given period of time
  • respiratory rate - noun the rate at which a person inhales and exhales; usually measured to obtain a quick evaluation of a person's health
  • restriction endonuclease - noun any of the enzymes that cut nucleic acid at specific restriction sites and produce restriction fragments; obtained from bacteria (where they cripple viral invaders); used in recombinant DNA technology
  • polymorphism - noun (biology) the existence of two or more forms of individuals within the same animal species (independent of sex differences); (chemistry) the existence of different kinds of crystal of the same chemical compound
  • resuscitation - noun the act of reviving a person and returning them to consciousness
  • retina - noun the light-sensitive membrane covering the back wall of the eyeball; it is continuous with the optic nerve
  • Rb - noun a soft silvery metallic element of the alkali metal group; burns in air and reacts violently in water; occurs in carnallite and lepidolite and pollucite
  • Retraction - noun the act of pulling or holding or drawing a part back; a disavowal or taking back of a previous assertion
  • retraction - noun the act of pulling or holding or drawing a part back; a disavowal or taking back of a previous assertion
  • reverse transcriptase - noun a polymerase that catalyzes the formation of DNA using RNA as a template; found especially in retroviruses
  • review article - noun an essay or article that gives a critical evaluation (as of a book or play)
  • rhizome - noun a horizontal plant stem with shoots above and roots below serving as a reproductive structure
  • rib - noun support resembling the rib of an animal; a projecting molding on the underside of a vault or ceiling; may be ornamental or structural; a riblike supporting or strengthening part of an animal or plant; any of the 12 pairs of curved arches of bone extending from the spine to or toward the sternum in humans (and similar bones in most vertebrates); a teasing remark; cut of meat including one or more ribs; verb form vertical ribs by knitting; subject to laughter or ridicule
  • ribonuclease - noun a transferase that catalyzes the hydrolysis of ribonucleic acid
  • ribonucleic acid - noun (biochemistry) a long linear polymer of nucleotides found in the nucleus but mainly in the cytoplasm of a cell where it is associated with microsomes; it transmits genetic information from DNA to the cytoplasm and controls certain chemical processes in the cell
  • RNA - noun (biochemistry) a long linear polymer of nucleotides found in the nucleus but mainly in the cytoplasm of a cell where it is associated with microsomes; it transmits genetic information from DNA to the cytoplasm and controls certain chemical processes in the cell
  • ribosome - noun an organelle in the cytoplasm of a living cell; they attach to mRNA and move down it one codon at a time and then stop until tRNA brings the required amino acid; when it reaches a stop codon it falls apart and releases the completed protein molecule for use by the cell
  • RISC - noun (computer science) a kind of computer architecture that has a relatively small set of computer instructions that it can perform
  • RISC - noun (computer science) a kind of computer architecture that has a relatively small set of computer instructions that it can perform
  • rod - noun any rod-shaped bacterium; a long thin implement made of metal or wood; visual receptor cell sensitive to dim light; a gangster's pistol; a square rod of land; a linear measure of 16.5 feet
  • root cap - noun thimble-shaped mass of cells covering and protecting the growing tip of a root
  • root hair - noun thin hairlike outgrowth of an epidermal cell just behind the tip; absorbs nutrients from the soil
  • rooted - adj. having roots of a specified sort; absolutely still
  • roughage - noun coarse food high in fiber but low in nutrients; its bulk stimulates peristalsis
  • ruminant - adj. related to or characteristic of animals of the suborder Ruminantia or any other animal that chews a cud; noun any of various cud-chewing hoofed mammals having a stomach divided into four (occasionally three) compartments
  • runner - noun fish of western Atlantic: Cape Cod to Brazil; device consisting of the parts on which something can slide along; a long narrow carpet; a person who is employed to deliver messages or documents; someone who travels on foot by running; a trained athlete who competes in foot races; a baseball player on the team at bat who is on base (or attempting to reach a base); someone who imports or exports without paying duties; a horizontal branch from the base of plant that produces new plants from buds at its tips
  • S - noun the 19th letter of the Roman alphabet; (thermodynamics) a thermodynamic quantity representing the amount of energy in a system that is no longer available for doing mechanical work; a unit of conductance equal to the reciprocal of an ohm; the cardinal compass point that is at 180 degrees; an abundant tasteless odorless multivalent nonmetallic element; best known in yellow crystals; occurs in many sulphide and sulphate minerals and even in native form (especially in volcanic regions); 1/60 of a minute; the basic unit of time adopted under the Systeme International d'Unites
  • salamander - noun any of various typically terrestrial amphibians that resemble lizards and that return to water only to breed; reptilian creature supposed to live in fire; fire iron consisting of a metal rod with a handle; used to stir a fire
  • sand - noun French writer known for works concerning women's rights and independence (1804-1876); a loose material consisting of grains of rock or coral; fortitude and determination; verb rub with sandpaper
  • saprobe - noun an organism that lives in and derives its nourishment from organic matter in stagnant or foul water
  • saprophyte - noun an organism that feeds on dead organic matter especially a fungus or bacterium
  • sarcolemma - noun an extensible membrane enclosing the contractile substance of a muscle fiber
  • sarcomere - noun one of the segments into which a myofibril is divided
  • Sargassum - noun brown algae with rounded bladders forming dense floating masses in tropical Atlantic waters as in the Sargasso Sea
  • saturated fatty acid - noun a fatty acid whose carbon chain cannot absorb any more hydrogen atoms; found chiefly in animal fats
  • scapula - noun either of two flat triangular bones one on each side of the shoulder in human beings
  • Schizophrenia - noun any of several psychotic disorders characterized by distortions of reality and disturbances of thought and language and withdrawal from social contact
  • schizophrenia - noun any of several psychotic disorders characterized by distortions of reality and disturbances of thought and language and withdrawal from social contact
  • Schwann cell - noun any cell that covers the nerve fibers in the peripheral nervous system and forms the myelin sheath
  • science - noun a particular branch of scientific knowledge; ability to produce solutions in some problem domain
  • scientific method - noun a method of investigation involving observation and theory to test scientific hypotheses
  • scion - noun a descendent or heir
  • scrotum - noun the external pouch that contains the testes
  • sebaceous gland - noun a cutaneous gland that secretes sebum (usually into a hair follicle) for lubricating hair and skin
  • secretin - noun peptic hormone produced by the mucous lining of the small intestine; can stimulate secretion by the pancreas and liver
  • seed - noun a mature fertilized plant ovule consisting of an embryo and its food source and having a protective coat or testa; a small hard fruit; the thick white fluid containing spermatozoa that is ejaculated by the male genital tract; anything that provides inspiration for later work; one of the outstanding players in a tournament; verb remove the seeds from; inoculate with microorganisms; sprinkle with silver iodide particles to disperse and cause rain; distribute (players or teams) so that outstanding teams or players will not meet in the early rounds; go to seed; shed seeds;bear seeds; help (an enterprise) in its early stages of development by providing seed money; place (seeds) in or on the ground for future growth
  • Self-pollination - noun fertilization by transfer of pollen from the anthers to the stigma of the same flower
  • self-pollination - noun fertilization by transfer of pollen from the anthers to the stigma of the same flower
  • Semen - noun the thick white fluid containing spermatozoa that is ejaculated by the male genital tract
  • semen - noun the thick white fluid containing spermatozoa that is ejaculated by the male genital tract
  • semilunar valve - noun a heart valve with cusps shaped like half-moons; prevents blood from flowing back into the heart
  • seminal vesicle - noun either of a pair of glands located on either side of the male urinary bladder that open into the vas deferens and that secrete many components of semen during ejaculation
  • seminiferous tubule - noun any of the numerous long convoluted tubules in the testis which are the sites where spermatozoa mature
  • senescence - noun the property characteristic of old age; the organic process of growing older and showing the effects of increasing age
  • sensory receptor - noun an organ having nerve endings (in the skin or viscera or eye or ear or nose or mouth) that respond to stimulation
  • system - noun instrumentality that combines interrelated interacting artifacts designed to work as a coherent entity; the living body considered as made up of interdependent components forming a unified whole; a group of physiologically or anatomically related organs or parts; a complex of methods or rules governing behavior;a procedure or process for obtaining an objective; a group of independent but interrelated elements comprising a unified whole;(physical chemistry) a sample of matter in which substances in different phases are in equilibrium; an ordered manner; orderliness by virtue of being methodical and well organized; an organized structure for arranging or classifying
  • sepal - noun one of the green parts that form the calyx of a flower
  • septum - noun (anatomy) a dividing partition between two tissues or cavities; a partition or wall especially in an ovary
  • serendipity - noun good luck in making unexpected and fortunate discoveries
  • Sertoli cell - noun elongated cells found in the seminiferous tubules of the testis; apparently they nourish the spermatids
  • serum - noun watery fluid of the blood that resembles plasma but contains fibrinogen
  • sesamoid bone - noun any of several small round bones formed in a tendon where it passes over a joint
  • sessile - adj. attached directly by the base; not having an intervening stalk; permanently attached to a substrate; not free to move about
  • set point - noun (tennis) the final point needed to win a set in tennis
  • seta - noun a stiff hair or bristle; stalk of a moss capsule
  • seta - noun a stiff hair or bristle; stalk of a moss capsule
  • chaeta - noun a stiff chitinous seta or bristle especially of an annelid worm
  • sex-linked - adj. concerning characteristics that are determined by genes carried on the sex chromosomes (on the X chromosome in particular)
  • sexual reproduction - noun reproduction involving the union or fusion of a male and a female gamete
  • short bone - noun a bone that is of approximately equal dimension in all directions
  • signal - adj. notably out of the ordinary; noun any communication that encodes a message; any incitement to action; an electric quantity (voltage or current or field strength) whose modulation represents coded information about the source from which it comes;verb be a signal for or a symptom of; communicate silently and non-verbally by signals or signs
  • silt - noun mud or clay or small rocks deposited by a river or lake;verb become chocked with silt
  • simple fruit - noun an indehiscent fruit derived from a single ovary having one or many seeds within a fleshy wall or pericarp: e.g. grape; tomato; cranberry
  • simple leaf - noun a leaf that is not divided into parts
  • sink - noun plumbing fixture consisting of a water basin fixed to a wall or floor and having a drainpipe; (technology) a process that acts to absorb or remove energy or a substance from a system; a covered cistern; waste water and sewage flow into it; a depression in the ground communicating with a subterranean passage (especially in limestone) and formed by solution or by collapse of a cavern roof; verb descend into or as if into some soft substance or place; pass into a specified state or condition; fall or drop to a lower place or level; cause to sink; go under, "The raft sank and its occupants drowned"; fall heavily or suddenly; decline markedly;embed deeply; fall or sink heavily; appear to move downward
  • SA - noun Nazi militia created by Hitler in 1921 that helped him to power but was eclipsed by the SS after 1943
  • node - noun (computer science) any computer that is hooked up to a computer network; any bulge or swelling of an anatomical structure or part; (astronomy) a point where an orbit crosses a plane; (physics) the point of minimum displacement in a periodic system; any thickened enlargement; a connecting point at which several lines come together; the source of lymph and lymphocytes
  • siphonophore - noun a floating or swimming oceanic colony of polyps often transparent or showily colored
  • skull - noun the bony skeleton of the head of vertebrates
  • small intestine - noun the longest part of the alimentary canal; where digestion is completed
  • Soil - noun the part of the earth's surface consisting of humus and disintegrated rock; the geographical area under the jurisdiction of a sovereign state; material in the top layer of the surface of the earth in which plants can grow (especially with reference to its quality or use); the state of being covered with unclean things; verb make soiled, filthy, or dirty
  • soil - noun the part of the earth's surface consisting of humus and disintegrated rock; the geographical area under the jurisdiction of a sovereign state; material in the top layer of the surface of the earth in which plants can grow (especially with reference to its quality or use); the state of being covered with unclean things; verb make soiled, filthy, or dirty
  • soil profile - noun a vertical section of soil from the ground surface to the parent rock
  • solute - noun the dissolved substance in a solution; the component of a solution that changes its state
  • solvent - adj. capable of meeting financial obligations; noun a liquid substance capable of dissolving other substances; a statement that solves a problem or explains how to solve the problem
  • somatic cell - noun any of the cells of a plant or animal except the reproductive cells; a cell that does not participate in the production of gametes
  • somite - noun one of a series of similar body segments into which some animals are divided longitudinally
  • source - noun a facility where something is available; anything that provides inspiration for later work; a document (or organization) from which information is obtained; (technology) a process by which energy or a substance enters a system; a publication (or a passage from a publication) that is referred to; the place where something begins, where it springs into being; anything (a person or animal or plant or substance) in which an infectious agent normally lives and multiplies; someone who originates or causes or initiates something;a person who supplies information; verb specify the origin of; get (a product) from another country or business
  • speciation - noun the evolution of a biological species
  • species - noun a specific kind of something; (biology) taxonomic group whose members can interbreed
  • spectrophotometer - noun a photometer for comparing two light radiations wavelength by wavelength
  • spermatophyte - noun plant that reproduces by means of seeds not spores
  • sphincter - noun a ring of muscle that contracts to close an opening
  • spicule - noun small pointed structure serving as a skeletal element in various marine and freshwater invertebrates e.g. sponges and corals
  • spinal cord - noun a major part of the central nervous system which conducts sensory and motor nerve impulses to and from the brain; a long tubelike structure extending from the base of the brain through the vertebral canal to the upper lumbar region
  • spinal nerve - noun any of the 31 pairs of nerves emerging from each side of the spinal cord (each attached to the cord by two roots: ventral and dorsal)
  • spirometry - noun the use of a spirometer to measure vital capacity
  • splicing - noun a junction where two things (as paper or film or magnetic tape) have been joined together
  • sporangium - noun organ containing or producing spores
  • spore - noun a small usually single-celled asexual reproductive body produced by many nonflowering plants and fungi and some bacteria and protozoans and that are capable of developing into a new individual without sexual fusion
  • sporophyll - noun leaf in ferns and mosses that bears the sporangia
  • sporophyte - noun the spore-producing individual or phase in the life cycle of a plant having alternation of generations
  • Squamata - noun diapsid reptiles: snakes and lizards
  • stamen - noun the male reproductive organ of a flower
  • stapes - noun the stirrup-shaped ossicle that transmits sound from the incus to the cochlea
  • starch - noun a complex carbohydrate found chiefly in seeds, fruits, tubers, roots and stem pith of plants, notably in corn, potatoes, wheat, and rice; an important foodstuff and used otherwise especially in adhesives and as fillers and stiffeners for paper and textiles; verb stiffen with starch
  • stele - noun an ancient upright stone slab bearing markings; the usually cylindrical central vascular portion of the axis of a vascular plant
  • stereoscopic vision - noun three-dimensional vision produced by the fusion of two slightly different views of a scene on each retina
  • sternum - noun the flat bone that articulates with the clavicles and the first seven pairs of ribs
  • steroid - noun any of several fat-soluble organic compounds having as a basis 17 carbon atoms in four rings; many have important physiological effects; any hormone affecting the development and growth of sex organs
  • stigma - noun a skin lesion that is a diagnostic sign of some disease; an external tracheal aperture in a terrestrial arthropod; the apical end of the style where deposited pollen enters the pistil; a symbol of disgrace or infamy
  • stipule - noun a small leafy outgrowth at the base of a leaf or its stalk; usually occurring in pairs and soon shed
  • stolon - noun a horizontal branch from the base of plant that produces new plants from buds at its tips
  • stoma - noun a mouth or mouthlike opening (especially one created by surgery on the surface of the body to create an opening to an internal organ); a minute epidermal pore in a leaf or stem through which gases and water vapor can pass
  • stomach - noun an enlarged and muscular saclike organ of the alimentary canal; the principal organ of digestion; an appetite for food; an inclination or liking for things involving conflict or difficulty or unpleasantness; the region of the body of a vertebrate between the thorax and the pelvis; verb bear to eat; put up with something or somebody unpleasant
  • strobilus - noun cone-shaped mass of ovule- or spore-bearing scales or bracts
  • stroma - noun the supporting tissue of an organ (as opposed to parenchyma); the dense colorless framework of a chloroplast; a mass of fungal tissue that has spore-bearing structures embedded in it or on it
  • style - noun a slender bristlelike or tubular process; a particular kind (as to appearance); editorial directions to be followed in spelling and punctuation and capitalization and typographical display; (botany) the narrow elongated part of the pistil between the ovary and the stigma; a pointed tool for writing or drawing or engraving; distinctive and stylish elegance; how something is done or how it happens; the popular taste at a given time; a way of expressing something (in language or art or music etc.) that is characteristic of a particular person or group of people or period; verb make consistent with certain rules of style; designate by an identifying term; make consistent with a certain fashion or style
  • subduction - noun a geological process in which one edge of a crustal plate is forced sideways and downward into the mantle below another plate
  • substrate - noun an indigenous language that contributes features to the language of an invading people who impose their language on the indigenous population; any stratum or layer lying underneath another; a surface on which an organism grows or is attached; the substance that is acted upon by an enzyme or ferment
  • sucrase - noun an enzyme that catalyzes the hydrolysis of sucrose into glucose and fructose
  • sulcus - noun (anatomy) any of the narrow grooves in an organ or tissue especially those that mark the convolutions on the surface of the brain
  • summation - noun the arithmetic operation of summing; calculating the sum of two or more numbers; a concluding summary (as in presenting a case before a law court); (physiology) the process whereby multiple stimuli can produce a response (in a muscle or nerve or other part) that one stimulus alone does not produce; the final aggregate
  • superior colliculus - noun an essential visual center between the retina and the striate cortex
  • superior vena cava - noun receives blood from the head and arms and chest and empties into the right atrium of the heart; formed from the azygos and both brachiocephalic veins
  • Supination - noun rotation of the hands and forearms so that the palms face upward
  • supination - noun rotation of the hands and forearms so that the palms face upward
  • surface tension - noun a phenomenon at the surface of a liquid caused by intermolecular forces
  • Surfactant - noun a substance capable of reducing the surface tension of a liquid in which it is dissolved
  • surfactant - noun a substance capable of reducing the surface tension of a liquid in which it is dissolved
  • suspensor - noun a support for the genitals worn by men engaging in strenuous exercise
  • sutural bone - noun any of the tiny soft bones found in the sutures between cranial bones
  • suture - noun thread of catgut or silk or wire used by surgeons to stitch tissues together; a seam used in surgery; an immovable joint (especially between the bones of the skull); verb join with a suture
  • Symbiosis - noun the relation between two different species of organisms that are interdependent; each gains benefits from the other
  • symbiosis - noun the relation between two different species of organisms that are interdependent; each gains benefits from the other
  • sympathetic nervous system - noun originates in the thoracic regions of the spinal cord; opposes physiological effects of the parasympathetic: reduces digestive secretions; speeds the heart; contracts blood vessels
  • symphysis - noun a growing together of parts or structures; an abnormal adhesion of two or more structures
  • synapse - noun the junction between two neurons (axon-to-dendrite) or between a neuron and a muscle
  • synapsid - noun extinct reptile having a single pair of lateral temporal openings in the skull
  • synapsis - noun the side by side pairing of homologous maternal and paternal chromosomes at the start of meiosis
  • syncytium - noun a mass of cytoplasm containing several nuclei and enclosed in a membrane but no internal cell boundaries (as in muscle fibers)
  • syrinx - noun the vocal organ of a bird; a primitive wind instrument consisting of several parallel pipes bound together
  • system - noun instrumentality that combines interrelated interacting artifacts designed to work as a coherent entity; the living body considered as made up of interdependent components forming a unified whole; a group of physiologically or anatomically related organs or parts; a complex of methods or rules governing behavior;a procedure or process for obtaining an objective; a group of independent but interrelated elements comprising a unified whole;(physical chemistry) a sample of matter in which substances in different phases are in equilibrium; an ordered manner; orderliness by virtue of being methodical and well organized; an organized structure for arranging or classifying
  • Systematics - noun the science of systematic classification
  • systematics - noun the science of systematic classification
  • systole - noun the contraction of the chambers of the heart (especially the ventricles) to drive blood into the aorta and pulmonary artery
  • T - noun the 20th letter of the Roman alphabet; hormone produced by the thyroid glands to regulate metabolism by controlling the rate of oxidation in cells; thyroid hormone similar to thyroxine but with one less iodine atom per molecule and produced in smaller quantity; exerts the same biological effects as thyroxine but is more potent and briefer; a unit of information equal to a trillion (1,099,511,627,776) bytes or 1024 gigabytes; a unit of weight equivalent to 1000 kilograms; one of the four nucleotides used in building DNA; all four nucleotides have a common phosphate group and a sugar (ribose); a base found in DNA (but not in RNA) and derived from pyrimidine; pairs with adenine
  • T cell - noun a small lymphocyte developed in the thymus; it orchestrates the immune system's response to infected or malignant cells
  • tadpole - noun a larval frog or toad
  • target cell - noun an abnormal red blood cell with the appearance of a dark ring surrounding a dark center; associated with anemia; any cell that has a specific receptor for an antigen or antibody or hormone or drug, or is the focus of contact by a virus or phagocyte or nerve fiber etc.
  • tarsal - adj. of or relating to or near the tarsus of the foot; noun any bone of the tarsus
  • taste bud - noun an oval sensory end organ on the surface of the tongue
  • taxis - noun the surgical procedure of manually restoring a displaced body part; a locomotor response toward or away from an external stimulus by a motile (and usually simple) organism
  • taxon - noun animal or plant group having natural relations
  • Taxonomy - noun practice of classifying plants and animals according to their presumed natural relationships; (biology) study of the general principles of scientific classification; a classification of organisms into groups based on similarities of structure or origin etc
  • taxonomy - noun practice of classifying plants and animals according to their presumed natural relationships; (biology) study of the general principles of scientific classification; a classification of organisms into groups based on similarities of structure or origin etc
  • telomerase - noun an enzyme in eukaryotic cells that can add telomeres to the ends of chromosomes after they divide
  • telomere - noun either (free) end of a eukaryotic chromosome
  • Telophase - noun the final stage of mitosis; the final stage of meiosis when the chromosomes move toward opposite ends of the nuclear spindle
  • telophase - noun the final stage of mitosis; the final stage of meiosis when the chromosomes move toward opposite ends of the nuclear spindle
  • temporal - adj. of this earth or world; not eternal; concerned with secular rather than sacred matters; of the material world; of or relating to the temples (the sides of the skull behind the orbit); of or relating to or limited by time; noun the semantic role of the noun phrase that designating the time of the state or action denoted by the verb
  • temporal lobe - noun that part of the cerebral cortex in either hemisphere of the brain lying inside the temples of the head
  • tendril - noun slender stemlike structure by which some twining plants attach themselves to an object for support
  • test - noun the act of testing something; the act of undergoing testing; any standardized procedure for measuring sensitivity or memory or intelligence or aptitude or personality etc; a hard outer covering as of some amoebas and sea urchins; trying something to find out about it; a set of questions or exercises evaluating skill or knowledge; verb undergo a test; determine the presence or properties of (a substance); achieve a certain score or rating on a test; put to the test, as for its quality, or give experimental use to;show a certain characteristic when tested; examine someone's knowledge of something; test or examine for the presence of disease or infection
  • test-cross - noun a cross between an organism whose genotype for a certain trait is unknown and an organism that is homozygous recessive for that trait so the unknown genotype can be determined from that of the offspring
  • testa - noun protective outer layer of seeds of flowering plants
  • Testosterone - noun a potent androgenic hormone produced chiefly by the testes; responsible for the development of male secondary sex characteristics
  • testosterone - noun a potent androgenic hormone produced chiefly by the testes; responsible for the development of male secondary sex characteristics
  • Tetrapod - noun a vertebrate animal having four feet or legs or leglike appendages
  • tetrapod - noun a vertebrate animal having four feet or legs or leglike appendages
  • thalamus - noun large egg-shaped structures of grey matter that form the dorsal subdivision of the diencephalon
  • Thalassemia - noun an inherited form of anemia caused by faulty synthesis of hemoglobin
  • thalassemia - noun an inherited form of anemia caused by faulty synthesis of hemoglobin
  • thallus - noun a plant body without true stems or roots or leaves or vascular system; characteristic of the thallophytes
  • theory - noun a belief that can guide behavior; a well-substantiated explanation of some aspect of the natural world; an organized system of accepted knowledge that applies in a variety of circumstances to explain a specific set of phenomena; a tentative theory about the natural world; a concept that is not yet verified but that if true would explain certain facts or phenomena
  • Thermodynamics - noun the branch of physics concerned with the conversion of different forms of energy
  • thermodynamics - noun the branch of physics concerned with the conversion of different forms of energy
  • theropod - noun any of numerous carnivorous dinosaurs of the Triassic to Cretaceous with short forelimbs that walked or ran on strong hind legs
  • thorn - noun a Germanic character of runic origin; something that causes irritation and annoyance; a small sharp-pointed tip resembling a spike on a stem or leaf
  • thymus - noun large genus of Old World mints: thyme; a ductless glandular organ at the base of the neck that produces lymphocytes and aids in producing immunity; atrophies with age
  • thyroglobulin - noun an iodine containing protein that is obtained from the thyroid gland and exhibits the general properties of the globulins
  • tibia - noun the inner and thicker of the two bones of the human leg between the knee and ankle
  • TV - noun an electronic device that receives television signals and displays them on a screen; broadcasting visual images of stationary or moving objects
  • TV - noun an electronic device that receives television signals and displays them on a screen; broadcasting visual images of stationary or moving objects
  • tissue - noun part of an organism consisting of an aggregate of cells having a similar structure and function; a soft thin (usually translucent) paper; verb create a piece of cloth by interlacing strands of fabric, such as wool or cotton
  • Tonicity - noun the elastic tension of living muscles, arteries, etc. that facilitate response to stimuli
  • tonicity - noun the elastic tension of living muscles, arteries, etc. that facilitate response to stimuli
  • Torpor - noun a state of motor and mental inactivity with a partial suspension of sensibility; inactivity resulting from lethargy and lack of vigor or energy
  • torpor - noun a state of motor and mental inactivity with a partial suspension of sensibility; inactivity resulting from lethargy and lack of vigor or energy
  • torsion - noun a twisting force; a tortuous and twisted shape or position
  • TLC - noun considerate and solicitous care
  • trabecula - noun rod-shaped structures of fibrous tissue that divide an organ into parts (as in the penis) or stabilize the structure of an organ (as in the spleen)
  • trachea - noun membranous tube with cartilaginous rings that conveys inhaled air from the larynx to the bronchi; one of the tubules forming the respiratory system of most insects and many arachnids
  • tracheid - noun long tubular cell peculiar to xylem
  • tracheophyte - noun green plant having a vascular system: ferns, gymnosperms, angiosperms
  • trait - noun a distinguishing feature of your personal nature
  • transcription - noun a sound or television recording (e.g., from a broadcast to a tape recording); something written, especially copied from one medium to another, as a typewritten version of dictation;(genetics) the organic process whereby the DNA sequence in a gene is copied into mRNA; the process whereby a base sequence of messenger RNA is synthesized on a template of complementary DNA; the act of making a record (especially an audio record); the act of arranging and adapting a piece of music
  • transduction - noun the process whereby a transducer accepts energy in one form and gives back related energy in a different form;(genetics) the process of transfering genetic material from one cell to another by a plasmid or bacteriophage
  • Transfer RNA - noun RNA molecules present in the cell (in at least 20 varieties, each variety capable of combining with a specific amino acid) that attach the correct amino acid to the protein chain that is being synthesized at the ribosome of the cell (according to directions coded in the mRNA)
  • tRNA - noun RNA molecules present in the cell (in at least 20 varieties, each variety capable of combining with a specific amino acid) that attach the correct amino acid to the protein chain that is being synthesized at the ribosome of the cell (according to directions coded in the mRNA)
  • transfer RNA - noun RNA molecules present in the cell (in at least 20 varieties, each variety capable of combining with a specific amino acid) that attach the correct amino acid to the protein chain that is being synthesized at the ribosome of the cell (according to directions coded in the mRNA)
  • tRNA - noun RNA molecules present in the cell (in at least 20 varieties, each variety capable of combining with a specific amino acid) that attach the correct amino acid to the protein chain that is being synthesized at the ribosome of the cell (according to directions coded in the mRNA)
  • transformation - noun the act of changing in form or shape or appearance; (genetics) modification of a cell or bacterium by the uptake and incorporation of exogenous DNA; a rule describing the conversion of one syntactic structure into another related syntactic structure; a qualitative change; (mathematics) a function that changes the position or direction of the axes of a coordinate system
  • Transitional - adj. of or relating to or characterized by transition
  • translation - noun the act of uniform movement; rewording something in less technical terminology; a written communication in a second language having the same meaning as the written communication in a first language; a uniform movement without rotation; (genetics) the process whereby genetic information coded in messenger RNA directs the formation of a specific protein at a ribosome in the cytoplasm; (mathematics) a transformation in which the origin of the coordinate system is moved to another position but the direction of each axis remains the same; the act of changing in form or shape or appearance
  • translational - adj. of or relating to uniform movement without rotation
  • translocation - noun (genetics) an exchange of chromosome parts;the transport of dissolved material within a plant
  • transpiration - noun the emission of water vapor from the leaves of plants; the passage of gases through fine tubes because of differences in pressure or temperature; the process of giving off or exhaling water vapor through the skin or mucous membranes
  • Transpiration - noun the emission of water vapor from the leaves of plants; the passage of gases through fine tubes because of differences in pressure or temperature; the process of giving off or exhaling water vapor through the skin or mucous membranes
  • transporter - noun a crane for moving material with dispatch as in loading and unloading ships; a long truck for carrying motor vehicles; a moving belt that transports objects (as in a factory)
  • transverse - adj. extending or lying across; in a crosswise direction; at right angles to the long axis
  • horizontal - adj. parallel to or in the plane of the horizon or a base line; noun something that is oriented horizontally
  • plane - adj. having a surface without slope, tilt in which no part is higher or lower than another; noun a carpenter's hand tool with an adjustable blade for smoothing or shaping wood; a power tool for smoothing or shaping wood; (mathematics) an unbounded two-dimensional shape; a level of existence or development; an aircraft that has a fixed wing and is powered by propellers or jets; verb cut or remove with or as if with a plane; make even or smooth, with or as with a carpenter's plane; travel on the surface of water
  • also - adv. in addition
  • triglyceride - noun glyceride occurring naturally in animal and vegetable tissues; it consists of three individual fatty acids bound together in a single large molecule; an important energy source forming much of the fat stored by the body
  • Triassic - adj. of or relating to or denoting the first period of the Mesozoic era; noun from 230 million to 190 million years ago; dinosaurs, marine reptiles; volcanic activity
  • Jurassic - adj. of or relating to or denoting the second period of the Mesozoic era; noun from 190 million to 135 million years ago; dinosaurs; conifers
  • tricuspid valve - noun valve with three cusps; situated between the right atrium and the right ventricle; allows blood to pass from atrium to ventricle and closes to prevent backflow when the ventricle contracts
  • triiodothyronine - noun thyroid hormone similar to thyroxine but with one less iodine atom per molecule and produced in smaller quantity; exerts the same biological effects as thyroxine but is more potent and briefer
  • triiodothyronine - noun thyroid hormone similar to thyroxine but with one less iodine atom per molecule and produced in smaller quantity; exerts the same biological effects as thyroxine but is more potent and briefer
  • T - noun the 20th letter of the Roman alphabet; hormone produced by the thyroid glands to regulate metabolism by controlling the rate of oxidation in cells; thyroid hormone similar to thyroxine but with one less iodine atom per molecule and produced in smaller quantity; exerts the same biological effects as thyroxine but is more potent and briefer; a unit of information equal to a trillion (1,099,511,627,776) bytes or 1024 gigabytes; a unit of weight equivalent to 1000 kilograms; one of the four nucleotides used in building DNA; all four nucleotides have a common phosphate group and a sugar (ribose); a base found in DNA (but not in RNA) and derived from pyrimidine; pairs with adenine
  • trisomy - noun chrosomal abnormality in which there is one more than the normal number of chromosomes in a cell
  • trophoblast - noun the membrane that forms the wall of the blastocyst in early development; aids implantation in the uterine wall
  • trypsin - noun an enzyme of pancreatic origin; catalyzes the hydrolysis of proteins to smaller polypeptide units
  • Tryptophan - noun an amino acid that occurs in proteins; is essential for growth and normal metabolism; a precursor of niacin
  • tryptophan - noun an amino acid that occurs in proteins; is essential for growth and normal metabolism; a precursor of niacin
  • tryptophan - noun an amino acid that occurs in proteins; is essential for growth and normal metabolism; a precursor of niacin
  • operon - noun a segment of DNA containing adjacent genes including structural genes and an operator gene and a regulatory gene
  • tuber - noun type genus of the Tuberaceae: fungi whose fruiting bodies are typically truffles; a fleshy underground stem or root serving for reproductive and food storage
  • tunicate - noun primitive marine animal having a saclike unsegmented body and a urochord that is conspicuous in the larva
  • tympanum - noun a large hemispherical brass or copper percussion instrument with a drumhead that can be tuned by adjusting the tension on it; the membrane in the ear that vibrates to sound; the main cavity of the ear; between the eardrum and the inner ear
  • U - adj. (chiefly British) of or appropriate to the upper classes especially in language use; noun the 21st letter of the Roman alphabet; a heavy toxic silvery-white radioactive metallic element; occurs in many isotopes; used for nuclear fuels and nuclear weapons; a base containing nitrogen that is found in RNA (but not in DNA) and derived from pyrimidine; pairs with adenine
  • ubiquinone - noun any of several quinones found in living cells and that function as coenzymes that transfer electrons from one molecule to another in cell respiration
  • ulna - noun the inner and longer of the two bones of the human forearm
  • ultrasound - noun very high frequency sound; used in ultrasonography; using the reflections of high-frequency sound waves to construct an image of a body organ (a sonogram); commonly used to observe fetal growth or study bodily organs
  • unsaturated - adj. (of color) not chromatically pure; diluted; used of a compound (especially of carbon) containing atoms sharing more than one valence bond; not saturated; capable of dissolving more of a substance at a given temperature
  • upstream - adj. in the direction against a stream's current; adv.toward the source or against the current
  • ureter - noun either of a pair of thick-walled tubes that carry urine from the kidney to the urinary bladder
  • uric acid - noun a white tasteless odorless crystalline product of protein metabolism; found in the blood and urine
  • urine - noun liquid excretory product
  • uropygial gland - noun oil-secreting gland situated at the base of the tail in most birds
  • uterus - noun a hollow muscular organ in the pelvic cavity of females; contains the developing fetus
  • V - noun the 22nd letter of the Roman alphabet; a unit of potential equal to the potential difference between two points on a conductor carrying a current of 1 ampere when the power dissipated between the two points is 1 watt; equivalent to the potential difference across a resistance of 1 ohm when 1 ampere of current flows through it; a soft silvery white toxic metallic element used in steel alloys; it occurs in several complex minerals including carnotite and vanadinite
  • vaccination - noun the scar left following inoculation with a vaccine;taking a vaccine as a precaution against contracting a disease
  • vaccine - noun immunogen consisting of a suspension of weakened or dead pathogenic cells injected in order to stimulate the production of antibodies
  • vacuole - noun a tiny cavity filled with fluid in the cytoplasm of a cell
  • vagina - noun the lower part of the female reproductive tract; a moist canal in female mammals extending from the labia minora to the uterus
  • variation - noun an activity that varies from a norm or standard; the act of changing or altering something slightly but noticeably from the norm or standard; an artifact that deviates from a norm or standard;a repetition of a musical theme in which it is modified or embellished; an instance of change; the rate or magnitude of change; (astronomy) any perturbation of the mean motion or orbit of a planet or satellite (especially a perturbation of the earth's moon);the process of varying or being varied; (ballet) a solo dance or dance figure; something a little different from others of the same type; (biology) an organism that has characteristics resulting from chromosomal alteration; the angle (at a particular location) between magnetic north and true north
  • vascular bundle - noun a unit strand of the vascular system in stems and leaves of higher plants consisting essentially of xylem and phloem
  • vascular plant - noun green plant having a vascular system: ferns, gymnosperms, angiosperms
  • vascular tissue - noun tissue that conducts water and nutrients through the plant body in higher plants
  • vasodilation - noun dilation of blood vessels (especially the arteries)
  • vasodilator - noun a drug that causes dilation of blood vessels
  • vasopressin - noun hormone secreted by the posterior pituitary gland (trade name Pitressin) and also by nerve endings in the hypothalamus; affects blood pressure by stimulating capillary muscles and reduces urine flow by affecting reabsorption of water by kidney tubules
  • vein - noun one of the horny ribs that stiffen and support the wing of an insect; a blood vessel that carries blood from the capillaries toward the heart; a distinctive style or manner; a layer of ore between layers of rock; any of the vascular bundles or ribs that form the branching framework of conducting and supporting tissues in a leaf or other plant organ; verb make a veinlike pattern
  • velum - noun a muscular flap that closes off the nasopharynx during swallowing or speaking; membrane initially completely investing the young sporophore of various mushrooms that is ruptured by growth; represented in the mature mushroom by a volva around lower part of stem and scales on upper surface of the cap; membrane of the young sporophore of various mushrooms extending from the margin of the cap to the stem and is ruptured by growth; represented in mature mushroom by an annulus around the stem and sometimes a cortina on the margin of the cap
  • vena cava - noun either of two large veins that return oxygen-depleted blood to the right atrium of the heart
  • venation - noun (zoology) the system of venous blood vessels in an animal; (botany) the arrangement of veins in a leaf
  • ventilation - noun the act of supplying fresh air and getting rid of foul air; a mechanical system in a building that provides fresh air;the bodily process of inhalation and exhalation; the process of taking in oxygen from inhaled air and releasing carbon dioxide by exhalation; free and open discussion of (or debate on) some question of public interest
  • perfusion - noun pumping a liquid into an organ or tissue (especially by way of blood vessels)
  • V - noun the 22nd letter of the Roman alphabet; a unit of potential equal to the potential difference between two points on a conductor carrying a current of 1 ampere when the power dissipated between the two points is 1 watt; equivalent to the potential difference across a resistance of 1 ohm when 1 ampere of current flows through it; a soft silvery white toxic metallic element used in steel alloys; it occurs in several complex minerals including carnotite and vanadinite
  • Q - noun the 17th letter of the Roman alphabet
  • mismatch - noun a bad or unsuitable match; verb match badly; match two objects or people that do not go together
  • ventricle - noun a chamber of the heart that receives blood from an atrium and pumps it to the arteries; one of four connected cavities in the brain; is continuous with the central canal of the spinal cord and contains cerebrospinal fluid
  • venule - noun a minute vein continuous with a capillary
  • vertebral column - noun the series of vertebrae forming the axis of the skeleton and protecting the spinal cord
  • Vertebrata - noun fishes; amphibians; reptiles; birds; mammals
  • vesicle - noun a small anatomically normal sac or bladderlike structure (especially one containing fluid)
  • vestibular sense - noun a sensory system located in structures of the inner ear that registers the orientation of the head
  • state - noun the way something is with respect to its main attributes;a politically organized body of people under a single government;the group of people comprising the government of a sovereign state;the territory occupied by one of the constituent administrative districts of a nation; a state of depression or agitation; the federal department in the United States that sets and maintains foreign policies; the territory occupied by a nation; (chemistry) the three traditional states of matter are solids (fixed shape and volume) and liquids (fixed volume and shaped by the container) and gases (filling the container); verb express in words; put before; indicate through a symbol, formula, etc.
  • virion - noun (virology) a complete viral particle; nucleic acid and capsid (and a lipid envelope in some viruses)
  • viroid - noun the smallest of viruses; a plant virus with its RNA arranged in a circular chromosome without a protein coat
  • Vision - noun the perceptual experience of seeing; a vivid mental image; a religious or mystical experience of a supernatural appearance; the formation of a mental image of something that is not perceived as real and is not present to the senses; the ability to see; the visual faculty
  • vision - noun the perceptual experience of seeing; a vivid mental image; a religious or mystical experience of a supernatural appearance; the formation of a mental image of something that is not perceived as real and is not present to the senses; the ability to see; the visual faculty
  • vital capacity - noun the maximum amount of air that can be exhaled after a maximum inhalation (usually tested with a spirometer); used to determine the condition of lung tissue
  • vitamin - noun any of a group of organic substances essential in small quantities to normal metabolism
  • W - noun the 23rd letter of the Roman alphabet; a unit of power equal to 1 joule per second; the power dissipated by a current of 1 ampere flowing across a resistance of 1 ohm; the cardinal compass point that is a 270 degrees; a heavy grey-white metallic element; the pure form is used mainly in electrical applications; it is found in several ores including wolframite and scheelite
  • w - noun the 23rd letter of the Roman alphabet; a unit of power equal to 1 joule per second; the power dissipated by a current of 1 ampere flowing across a resistance of 1 ohm; the cardinal compass point that is a 270 degrees; a heavy grey-white metallic element; the pure form is used mainly in electrical applications; it is found in several ores including wolframite and scheelite
  • water vascular system - noun system of fluid-filled tubes used by echinoderms in locomotion and feeding and respiration
  • wavelength - noun the distance (measured in the direction of propagation) between two points in the same phase in consecutive cycles of a wave; a shared orientation leading to mutual understanding
  • Wax - noun any of various substances of either mineral origin or plant or animal origin; they are solid at normal temperatures and insoluble in water; verb go up or advance; increase in phase; cover with wax
  • wax - noun any of various substances of either mineral origin or plant or animal origin; they are solid at normal temperatures and insoluble in water; verb go up or advance; increase in phase; cover with wax
  • weather - adj. towards the side exposed to wind; noun the meteorological conditions: temperature and wind and clouds and precipitation; verb change under the action or influence of the weather; sail to the windward of; cause to slope; face or endure with courage
  • whisk fern - noun chiefly tropical clump-forming plants of skeletal appearance resembling whisk brooms; lacking roots
  • white blood cell - noun blood cells that engulf and digest bacteria and fungi; an important part of the body's defense system
  • X - noun the 24th letter of the Roman alphabet; street names for methylenedioxymethamphetamine
  • X-linked - adj. relating to genes or characteristics or conditions carried on the X chromosome
  • Xylem - noun the woody part of plants: the supporting and water-conducting tissue, consisting primarily of tracheids and vessels
  • xylem - noun the woody part of plants: the supporting and water-conducting tissue, consisting primarily of tracheids and vessels
  • Y - noun the 25th letter of the Roman alphabet; a silvery metallic element that is common in rare-earth minerals; used in magnesium and aluminum alloys
  • yeast - noun any of various single-celled fungi that reproduce asexually by budding or division; a commercial leavening agent containing yeast cells; used to raise the dough in making bread and for fermenting beer or whiskey
  • yolk sac - noun membranous structure enclosing the yolk of eggs in birds reptiles marsupials and some fishes; circulates nutrients to the developing embryo; membranous structure that functions as the circulatory system in mammal embryos until the heart becomes functional
  • Z - noun the 26th letter of the Roman alphabet; the ending of a series or sequence
  • zona pellucida - noun thick membrane around the mammalian ovum; can be penetrated by one sperm in the fertilization process; usually remains around the fertilized egg until it is implanted in the wall of the uterus
  • Zoology - noun the branch of biology that studies animals; all the animal life in a particular region or period
  • zoology - noun the branch of biology that studies animals; all the animal life in a particular region or period
  • zoonosis - noun an animal disease that can be transmitted to humans
  • Zooplankton - noun animal constituent of plankton; mainly small crustaceans and fish larvae
  • Zygomycota - noun division of fungi having sexually produced zygospores
  • zygospore - noun a plant spore formed by two similar sexual cells


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