ABC transporter See transporter, ABC.

ABL oncogene See oncogene, ABL.

ABO blood group system See blood group system, ABO.

Ad4BP See adrenal 4 binding protein.

A/D ratio Ratio of the adult toxic dose to the developmentally toxic dose. [ref. 5]

AMPA receptor See receptor, 2-amino-3-(3-hydroxy-5-methyl-1,2-oxazol-4-yl)propanoic acid (AMPA).

ANCA-associated vasculitis See vasculitis, antineutrophil cytoplasmic autoantibody-associated vasculitis.

APECED syndrome See polyendocrinopathy, autoimmune.

ATP See adenosine triphosphate.

abdomen (n)/abdominal (adj)

1. Part of the body between the thorax and the pelvis in vertebrates.

2. Most posterior segment of the insect body.

[*]

abdominal cavity See cavity, abdominal.

abiological See abiotic.

abiotic abiological Opposite term: biotic.

Not associated with living organisms. [ref. 1]

abiotic degradation See degradation, abiotic.

abiotic transformation See transformation, abiotic.

ablepharia (n)/ablepharous (adj) Congenital absence of the eyelids. [ref. 5]

abortifacient Substance that causes pregnancy to end prematurely and causes an abortion. [ref. 1]

abortion, induced Intentional termination of a pregnancy with death of the embryo or fetus. [ref. 5]

abortion, spontaneous miscarriage

Unintentional termination of pregnancy before the embryo or fetus has developed to the stage of independent viability, or in humans before the 20th week of gestation. [ref. 5]

absolute bioavailability See bioavailability, absolute.

absolute fitness See fitness.

absolute lethal concentration (LC100) See lethal concentration, absolute

absolute lethal dose (LD100) See lethal dose, absolute.

absolute risk See risk, absolute.

absorbance (A)

Logarithm of the ratio of incident to transmitted radiant power through a sample (excluding the effects of sample cell walls).

Note 1: Depending on the base of the logarithm, decadic and Napierian absorbances are used. Symbols: A, A10, Ae.

Note 2: Absorbance is sometimes called extinction, although the term ''extinction'', better called attenuance, is reserved for the quantity that takes into account the effects of luminescence and scattering as well.

Note 3: When natural logarithms are used, the Napierian absorbance is the logarithm to the base e of the incident spectral radiant power, essentially monochromatic, divided by the transmitted spectral radiant power, P?. [ref. 1]

absorbate Substance that enters and is retained inside a solid or semisolid matrix (absorbent). [ref. 2]

absorbed dose (of a substance) See dose, absorbed.

absorbed dose (of ionizing radiation)

Energy imparted by ionizing radiation to a specified volume of matter divided by the mass of that volume. [ref. 1]

absorbent Solid or semisolid matrix that is able to accommodate and retain an absorbate. [ref. 2]

See also sorbate; sorbent.

absorptance (in chemistry), a

Absorbed radiant power divided by the incident radiant power. Also called absorption factor. When a = 1, a ˜ Ae, where Ae is the Napierian absorbance. [ref. 1]

See also absorbance.

absorption (general)

1. Process of one material (absorbate) being retained by another (absorbent). Note: Absorption may be the physical solution of a gas, liquid, or solid in a liquid, attachment of molecules of a gas, vapor, liquid, or dissolved substance to a solid surface by physical forces, etc.

2. Transfer of some or all of the energy of radiation to matter that it traverses. Note: Absorption of light at bands of characteristic wavelengths is used as an analytical method in spectrophotometry to identify the chemical nature of molecules, atoms, or ions and to measure the concentrations of these chemical species.

[ref. 2]

See also adsorption; sorption.

absorption (in biology) uptake

Penetration of a substance into an organism and its cells by various processes, some specialized, some involving expenditure of energy (active transport), some involving a carrier system, and others involving passive movement down an electrochemical gradient (passive transport).

Note: In mammals, absorption is usually through the respiratory tract, gastrointestinal tract, or skin into the circulatory system and from the circulation into organs, tissues, and cells. [ref. 2]

absorption (of radiation)

Phenomenon in which radiation transfers some or all of its energy to matter that it traverses.

[ref. 1]

absorption, systemic

Uptake to the blood and transport via the blood of a substance to one or more organs or compartments in the body distant from the site of absorption.

[ref. 2]

absorption coefficient (in biology) absorption factor

Absorbed quantity (uptake) of a substance divided by the administered quantity (intake).

Note: For exposure by way of the respiratory tract, the absorption coefficient is the ratio of the absorbed amount to the amount of the substance (usually particles) deposited (adsorbed) in the lungs. [ref. 1]

absorption factor See absorptance (in chemistry); absorption coefficient (in biology).

abundance

1. Total number of individual organisms in a population, seen over a defined period of time in a certain place.

Note: For abundance of fish, an estimate of total weight may replace number.

2....