Annular spaceA ring-shaped space located between two circular objects, such as two pipes.
AnodeThe positive pole or electrode of an electrolytic cell, vacuum tube, etc. (see also sacrificial anode).
anomaliesThe departures of temperature, precipitation, or other weather elements from long-term averages.
ANOMALOUS PROPAGATION (AP)Non-standard atmospheric temperature or moisture gradients will cause all or part of the radar beam to propagate along a non-normal path.
AnomalySomething that is out of the ordinary. For example if in a set of 1000 two winged, two legged, one headed, (essentially normal) chickens, one of them had…
anonymous DNA markerA detectable by virtue of variation in its sequence. The function (if any) of the sequence is unknown.
ANSIAmerican National Standards Institute - a private, non-profit organization that administers and coordinates the U.S.
antagonismAn interaction between two organisms (e.g. moulds or bacteria) in which the growth of one is inhibited by the other. Opposite: synergism.
antagonistIn medicine, a substance that stops the action or effect of another substance. For example, a drug that blocks the stimulating effect of estrogen on a…
Antarctic "Ozone Hole"Refers to the seasonal depletion of stratospheric ozone in a large area over Antarctica. See ozone, ozone layer.
Antecedent floodA flood or series of floods assumed to occur prior to the occurrence of an inflow design flood (IDF).
ANTENNA GAINThe measure of effectiveness of a directional antenna as compared to an isotropic radiator, maximum value is called antenna gain by convention.
Anterior visceral endoderm (AVE)Specific tissue structure arising in the early embryo that helps establish the anterior-posterior axis of the organism.
AnthelionA luminous white spot that appears on the parhelic circle at the same altitude as the sun and 180 degrees from it in azimuth.
antherThe upper part of a stamen, containing pollen sacs within which the pollen develops and matures.
anther cultureThe aseptic culture of immature anthers to generate haploid plants from microspores via androgenesis.
anthesisThe period during which anthers bear mature and functional pollen.
anthocyaninA water-soluble blue, purple or red flavonoid pigments found in vacuoles of cells of certain plants.
AnthraciteA hard, black, lustrous coal containing a high percentage of fixed carbon and a low percentage of volatile matter. Often referred to as hard coal.
Anthracite (coal)A hard, dense type of coal, that is hard to break, clean to handle, difficult to ignite, and that burns with an intense flame and with the virtual absence…
AnthropogenicReferring to alterations in the environment due to the presence or activities of humans.
Anthropogenic emissionsMade by people or resulting from human activities. Usually used in the context of emissions that are produced as a result of human activities.
AnthropomorphicDescribed or thought of as having human form or human attributes.
AnthropomorphismAscribing human qualities, characteristics, or behavior to inanimate objects, animals, or natural phenomena.
anti-idiotype antibodyAn antibody, produced by an organism, which specifically binds to the binding site of an antibody developed by that organism against a foreign antigen.
Anti-Seep CollarA projecting collar of steel or concrete built around the outside of a pipe, tunnel, or conduit under or through an embankment dam to lengthen the seep…
anti-terminatorA protein which enables RNA polymerase to ignore certain transcriptional stop or termination signals and thereby produce longer than normal transcripts.
Anti-windThe upper or return branch of an along-valley wind system, as confined within a valley, and blowing in a direction opposite to the winds in the lower…
antiauxinA chemical that interferes with the auxin response, sometimes by the prevention of auxin transport. Some antiauxins may promote morphogenesis in vitro (e.
antibiosisThe prevention of growth or development of an organism by a substance or another organism.
AntibioticA drug used to treat infections caused by bacteria and other microorganisms. Atrial Fibrillation: A heart rhythm disorder (arrhythmia) that usually…
Antibiotic resistanceThe ability of a microorganism to produce a protein that disables an antibiotic or prevents transport of the antibiotic into the cell.
antibiotic resistance marker gene(Abbreviation: ARMG). Genes (usually of bacterial origin) used as selection markers in transgenesis, because their presence allows cell survival in the…
Antibody(AN-tee-BAH-dee) A type of protein made by plasma cells (a type of white blood cell) in response to an antigen (foreign substance).
Antibody (Immunoglobulin)A protein produced by the white blood cells (leukocytes) to battle foreign substances, such as bacteria, that enter the body.
antibody binding siteThe part of an antibody that binds to the antigenic determinant. See: complementarity-determining regions. Synonym: paratope.
antibody classThe class to which an antibody belongs, depending on the type of heavy chain present.
antibody structureDescribes the molecular architecture of an antibody, which consists of two identical "light" chains and two identical "heavy" chains and has two antigen…
antibody-mediated immune responseThe synthesis of antibodies by B cells in response to an encounter of the cells of the immune system with a foreign antigen.
AnticipationA situation that exists when claimed invention is not novel in view of the prior art.
anticlinalThe orientation of cell wall or plane of cell division perpendicular to the surface. Opposite: periclinal.
AnticlineA fold in rocks that curves upward in a convex way. Upward fold in rock layers that creates an arched or domelike uplift of sedimentary layers.
anticoding strandThe DNA strand used as template for transcription. The resulting mRNA is complementary in sequence to that of the anticoding strand.
AnticodonA nucleotide base triplet in a transfer RNA molecule that pairs with a complementary base triplet, or codon, in a messenger RNA molecule.
AnticyclogenesisThe formation or intensification of an anticyclone or high pressure center.
AnticycloneA large-scale circulation of winds around a central region of high atmospheric pressure, clockwise in the Northern Hemisphere, counterclockwise in the…
Anticyclonic circulationAnticyclonic circulation System of air movements (atmospheric circulation) associated with an anticyclone, which is clockwise in the Northern Hemisphere…
Anticyclonic RotationRotation in the opposite sense as the Earth's rotation, i.e., clockwise in the Northern Hemisphere as would be seen from above.
Antifreeze SolutionA fluid, such as methanol or ethylene glycol, added to vehicle engine coolant, or used in solar heating system heat transfer fluids, to protect the…
AntigenA substance that causes the immune system to make a specific immune response.
Antigen presenting cells (APCs)One of a variety of cells within the body that can process antigens and display them on their surface in a form recognizable by T cells.
Antigenic determinantA surface feature of a microorganism or macromolecule, such as a glycoprotein, that elicits an immune response.
Antigenic switchingThe altering of a microorganism's surface antigens through genetic rearrangement, to elude detection by the host's immune system.
antihaemophilic globulin(Abbreviation AHG). One of the blood clotting factors, a soluble protein that causes the fibrin matrix of a blood clot to form.
Antilles CurrentA current which originates in the vicinity of the Leeward Islands as part of the Atlantic North Equatorial Current.
AntimatterMatter made up of elementary particles whose masses are identical to their normal-matter counterparts but whose other properties, such as electric charge…
Antimicrobial agentAny chemical or biological agent that harms the growth of microorganisms.
antinutrientCompounds that inhibit the normal uptake or utilization of nutrients.
antioxidant(AN-tee-OK-sih-dent) A substance that protects cells from the damage caused by free radicals (unstable molecules made by the process of oxidation during…
antiparallel orientationThe normal arrangement of the two strands of a double-stranded DNA molecule, and of other nucleic-acid duplexes (DNA -RNA, RNA -RNA ), in which the two…
Antiparticle/antiquark/antielectronFor most particle types there is another particle type that has exactly the same mass but the opposite value of all other charges.
Antireflection CoatingA thin coating of a material applied to a photovoltaic cell surface that reduces the light reflection and increases light transmission.
AntisenseThe non-coding strand in double-stranded DNA. The antisense strand serves as the template for mRNA synthesis. See also cell
antisense DNA(AN-tee-sents â¦) Small pieces of DNA that can bind to specific molecules of RNA and block the cell's ability to use the RNA to make a protein.
antisense geneA gene that produces an mRNA complementary to the transcript of a normal gene (usually constructed by inverting the coding region relative to the promoter…
antisense RNA(AN-tee-sents â¦) Small pieces of RNA that can bind to specific molecules of RNA and block the cell's ability to use the RNA to make a protein.
antisense therapyThe in vivo treatment of a genetic disease by blocking translation of a protein with a DNA or an RNA sequence that is complementary to a specific mRNA.
antisepticAny substance that kills or inhibits the growth of disease-causing micro-organism (a micro-organism capable of causing sepsis), but is essentially…
antiserumThe fluid portion of the blood of an immunized animal (after coagulation of the blood), which retains any antibodies.
antitranspirantA compound designed to reduce plant transpiration. Applied to the leaves of newly transplanted trees, shrubs etc., or cuttings in lieu of misting.
antixenosisThe modification of the behaviour of an organism by a substance or another organism.
AnvilThe flat, spreading top of a cumulonimbus cloud, often shaped like an anvil. Thunderstorm anvils may spread hundreds of miles downwind from the…
Anvil Crawler[Slang], a lightning discharge occurring within the anvil of a thunderstorm, characterized by one or more channels that appear to crawl along the…
Anvil DomeA large overshooting top or penetrating top.
Anvil RolloverSlang for a circular or semicircular lip of clouds along the underside of the upwind part of a back-sheared anvil, indicating rapid expansion of the anvil.
Anvil ZitsSlang for frequent (often continuous or nearly continuous), localized lightning discharges occurring from within a thunderstorm anvil.
ApertureAn opening; in solar collectors, the area through which solar radiation is admitted and directed to the absorber.
APEXThe portion of a root or shoot containing the primary or apical meristem.
AphelionThe point on the annual orbit of a body (about the sun) that is farthest from the sun; at present, the earth reaches this point (152 million kilometer…
ApheresisA procedure in which blood is collected, part of the blood such as platelets or white blood cells is taken out, and the rest of the blood is returned to…
API MethodA statistical method to estimate the amount of surface runoff which will occur from a basin from a given rainstorm based on the antecedent precipitation…
apical cellA meristematic initial in the apical meristem of shoots or roots of plants.