AL - Aluminum
Alternating Current (ac) - A flow of electricity which reaches maximum in one direction, decreases to zero, then reverses itself and reaches maximum in the opposite direction. The cycle is repeated continuously. The number of cycles per second is equal to the frequency.
Ambient Temperature - The temperature of the atmosphere of surrounding environment. Typically defined by industry standards as 25° C.
Amp (Ampere) - A unit that measures the strength/rate of flow of electrical current.
ANSI - American National Standards Institute; Electrical standard developed and published as a result of recommended practices and studies made by NEMA and IEEE.
Arc - Sparking that results when undesired current flows between two point of differing potential.
Arc Voltage - The reaction of a circuit's inductance to the rate of current change in the circuit; E = L(di/dt); when a current-limiting fuse operates, there is an associated arc voltage on the system.
Armored Cable - Electrical wires protected by metal sheathing.
Arrester - A protective device for limiting surge voltages on equipment by diverting surge current and returning the device to its original status. It is capable of repeating these functions as specified.
Aught - Standard conductor size, i.e. 4 aught designation 4/0.

Branch Circuits - The circuits in a house that branch from the service panel to boxes and devices.
Breakdown Voltage - Voltage at which material fails.
Breaker - A switch-like device that connects/disconnects power to a circuit.
Buss Bar - Separate, metallic strips that extend through the service panel. Breakers slide onto the "hot" busses and neutral and ground wires screw down in their respective busses.
BX Cable - An old type of armored cable now illegal.

Capacitor - An electrical device used to store electrical energy, and to release it back into the power system when required.
Cable Clamps - Metal clips inside an electrical box that hold wires in place.
Circuit - A continuous loop of current (i.e. incoming "hot" wire, through a device, and returned by "neutral" wire).
Circuit Breaker - The most common type of "overcurrent protection." A breaker trips when a circuit becomes overloaded or shorts out.
Conductor - Any material which allows electrons to flow through it.
Conduit - A protective metal tube that wires run through.
CU - Copper.
Current - The movement of electrons through a conductor, measured in amperes.
Current Interrupter - Any device that will open a circuit after sensing an abnormal high-circuit condition; a general name given to all types of fuses, reclosers and breakers.