AdsorbateThe material being removed by the adsorption process.
Adsorbed waterWater in a soil or rock mass, held by physico-chemical forces, having physical properties substantially different from absorbed water or chemically…
AdsorbentThe material (for example activated carbon) that is responsible for removing the undesirable substance in the adsorption process.
AdsorptionThe adhesion, in an extremely thin layer, of molecules (as in gases, solutions, or liquids) to the surface of solid bodies or liquids with which they are…
Adult (or somatic) stem cellStem cells found in different tissues of the developed, adult organism that remain in an undifferentiated, or unspecialized, state.
Advanced Decision Support System (ADSS)Computer software designed to provide easy access to and allow efficient use of methods of analysis and information management.
Advanced Technology VehiclesA vehicle that combines new engine, power, or drivetrain systems to significantly improve fuel economy.
ADVCTNAdvection- Transport of an atmospheric property by the wind.
Advection(Abbrev. ADVCTN)- Transport of an atmospheric property by the wind.
Advection FogA fog that forms when warm air flows over a cold surface and cools from below until saturation is reached.
advective tendencyThe large-scale advective tendency of temperature and moisture used to force SCMs and CSRMs, derived from constrained variational analysis.
adventitiousA structure arising at sites other than the usual ones, e.g. shoots from roots or leaves, and embryos from any cell other than a zygote.
ADVISA program which combines the Antecedent Precipitation Index (API) method of estimating runoff with unit hydrograph theory to estimate streamflow for a…
Advisory(Abbrev. ADVY)- Highlights special weather conditions that are less serious than a warning.
AerationThe process of adding air to water by either passing air through water or passing water through air.
Aeration basinA basin where oxygen is supplied by mechanical agitation or pneumatic means to enhance the breakdown of wastes held in suspension.
Aeration ZoneA portion of the lithosphere in which the functional interstices of permeable rock or earth are not filled with water under hydrostatic pressure.
Aerial coverGround area circumscribed by the perimeter of the branches and leaves of a given plant or group of plants (generally used as a measure of relative…
AERMODA refined, steady-state plume model that incorporates air dispersion on the basis of a state-of-the-art planetary boundary layer turbulence structure and…
AeroallergensAny of a variety of allergens such as pollens, grasses, or dust carried by winds.
AerobeA microorganism that grows in the presence of oxygen. See Anaerobe.
AerobicIn biochemistry, reactions that need oxygen to happen or happen when oxygen is present.
Aerobic BacteriaMicroorganisms that require free oxygen, or air, to live, and that which contribute to the decomposition of organic material in soil or composting systems.
aerobic respirationA chemical process in which oxygen is used to make energy from carbohydrates (sugars).
AerosolA system of colloidal particles dispersed in a gas, such as smoke or fog.
aerosol absorptionThe process in which radiation energy is retained by aerosols.
aerosol Angstrom coefficientOften incorrectly used synonymously with "aerosol Angstrom exponent", but should instead refer to the aerosol optical depth at the reference wavelength (1…
aerosol Angstrom exponentThe exponent of the inverse power-law that approximates the wavelength dependence of aerosol optical depth.
AFDArea Forecast Discussion - This National Weather Service product is intended to provide a well-reasoned discussion of the meteorological thinking which…
Affected EnvironmentFor an environmental impact statement, a description of the existing environment covering information necessary to assess or understand the impacts.
Affected relative pairIndividuals related by blood, each of whom is affected with the same trait. Examples are affected sibling, cousin, and avuncular pairs.
affinity chromatographyA method for purifying specific components in a solution by exploiting their specific binding to known molecule(s).
affinity tagAn amino acid sequence that has been engineered into a protein to make its purification easier.
AfforestationPlanting of new forests on lands that historically have not contained forests.
AfforestationsPlanting of new forests on lands that have not been recently forested.
aflatoxinsA group of toxic compounds, produced by Aspergillus flavus, that bind to DNA and prevent replication and transcription.
AFLPAbbreviation for amplified fragment length polymorphism.
AfterbayThe tail race of a hydroelectric power plant at the outlet of the turbines. The term may be applied to a short stretch of stream or conduit, or to a pond…
Afterbay (tailrace)The body of water immediately downstream from a powerplant or pumping plant. A reservoir or pool that regulates fluctuating discharges from a…
Afterbay dam (reregulating dam)A dam located downstream from a large hydroelectric powerplant used to regulate discharges downstream. See regulating dam.
AftershocksEarthquakes that follow the largest shock of an earthquake sequence. They are smaller than the main shock and within one to two rupture lengths distance…
Agarose gel electrophoresisA matrix composed of a highly purified form of agar that is used to separate larger DNA and RNA molecules ranging 20,000 nucleotides. (See Electrophoresis.
AgglomerateAn ice cover of floe formed by the freezing together of various forms of ice.
AggradationGeologic process wherein streambeds, floodplains, sandbars, and the bottom of water bodies are raised in elevation by the deposition of sediment; the…
Aggregate1. A clump or mass formed by gathering or collecting units. 2. A body of loosely associated cells, such as a friable callus or cell suspension. 3.
Aggregation techniqueA technique used in model organism studies in which embryos at the 8-cell stage of development are pushed together to yield a single embryo (used as an…
agonistA drug that triggers an action from a cell or another drug.
Agricultural Districts/Preservation AreasAreas designed to keep land in agriculture that are legally recognized. Landowners may voluntarily enroll in programs and may receive special benefits and…
Agricultural drainageThe process of directing excess water away from root zones by natural or artificial means, such as by using a system of pipes and drains placed below…
Agricultural firesFires ignited to meet specific management objectives on agricultural lands.