A/C

(Abbreviation)
Across Corners: Distance on a nut or bolt head from one corner to the opposite corner.
Usage: Determines the size of a hole needed to insert a recessed nut or bolt head.

Alternating Current: Electrical current that periodically reverses direction.

Air Conditioning/Air Conditioner: System for cooling and dehumidifying indoor air.

Actinium: Chemical element with symbol “Ac”.

Transformation Temperature: Temperature at which phase changes occur in iron or steel.
Examples: Ac1 (eutectoid) and Ac3 (ferrite/austenite phase boundary).

Asphaltic Concrete: Mixture of asphalt cement, graded aggregate, mineral filler, and additives.