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AAR - American Association of Railroads

Abrasion Resistance - Ability of a wire, cable or material to resist surface wear.

Accelerated Life Test - An accelerated life test is a test in which certain factors such as voltage, temperature, etc. to which a cable is subjected are increased in magnitude above normal operating values to obtain observable deterioration in a reasonable period of time and thereby afford some measure of the probable cable life under operating voltage, temperature, etc.

Acccelerator - A chemical additive which hastens a chemical reaction under specific conditions. A.C. Resistance - The total resistance offered by a device in an alternating current circuit due to inductive and capacitive effects, as well as the direct current resistance.

Activator - A chemical additive used to initiate the chemical reaction in a specific chemical mixture

Active Current - In an alternating current, a component in phase with the voltage; the working component as distinguished from the idle or wattles component.

Active Pressure - In an A.C. circuit, the pressure which produces a current, as distinguished from the voltage impressed upon the circuit.

Admittance - The measure of the ease with which an alternating current flows in a circuit. The reciprocal of impedance.

Adhesion - The state in which two surfaces are held together by interfacial forces which may be chemical or mechanical in nature.

Aging - The irreversible change in properties or appearance of a material with time and under specific conditions (usually accelerated representations of environmental states, such as high temperature, oxygen or other carious conditions).