A-arm:
A suspension linkage formed in the shape of an "A" or "V" found commonly on the front suspension. The sides of the two legs of the A-arm are connected to the chassis by rubber bushings and the peak of the A-arm is attached to the wheel assembly. In this way, the wheel can freely move up and down. Sometimes there is an upper A-arm, a lower A-arm, or both upper and lower A-arms. The British call it a "wishbone."

Abacus:
1. The uppermost part of a column capital or pilaster, on which the architrave rests.
2. A bead frame. Used as an arithmetic calculating aid.

Abampere:
A unit of electric current in the CGS electromagnetic system of units. One abampere equals 10A.

Aabamurus:
A supporting wall or buttress, built to add strength to another wall.

Aabandonment:
A voluntary surrender of legal rights or title to a mining claim.

Aabatjour:
An opening to admit light and generally to deflect it downwards; a skylight

Aabaxial:
Rays of light which do not coincide with the optical axis of a lens system.

Aabbe refractometer:
An instrument for measuring directly the refractive index of liquids, minerals, and gemstones.

Accelerator
Gas pedal or throttle. A foot-operated pedal or hand-operated lever connected by linkage or a cable to the throttle plate in the carburetor.

Actual Cash Value
The amount of money invested in the purchase and repairs of a used vehicle. Also known as ACV, this represents the amount of out of pocket expense a dealer or broker is "into" a car.

Afterboil
The boiling of engine coolant after the engine is stopped.

Aftermarket (Replacement Market)
all products and services used in the repair and maintenance of vehicles that was not produced by the original car manufacturer.

Afterruning
(Also called run-on and dieseling) When engine continues to operate after the ignition switch is turned off, can be destructive to an engine

Agent or broker
an intermediary with legal authority to operate on behalf of the manufacturer.

A.I.R
Air Injection Reactor

Air Bag
The air bag, also known as a Supplemental Inflatable Restraint System, is a passive safety device, supplemental to safety belts, that inflates to provide a cushion to absorb impact forces during moderate to severe frontal collisions. This system can help to lessen the chance of contact with the steering wheel, instrument panel and windshield. The air bag is actuated automatically by sensors located in the front of the vehicle. To maximize effectiveness, seat and shoulder belts must always be used in conjunction with this system

Air Gap
Space between the spark plug electrodes, also known as gap, often adjusted to gain maximum performance.

Airfoil
An aerodynamic device designed to improve traction by increasing the downforce on the car. The use of airfoils (also called wings) increases the cornering capability and improves stability at speed, but often at the expense of additional aerodynamic drag.

Air Injection
A system that injects air into the exhaust ports of the engine for combustion of unburned hydrocarbons in the exhaust gases, thus producing "cleaner" exhaust emissions.

Alignment
Generally refers to wheel alignment, which is the proper adjustment of the car's front and rear suspension for camber, toe, caster and ride height.

A-Pillar
In the side view, the foremost roof support of a vehicle, located in most instances between the outer edge of the windshield and the leading edge of the front door upper. Also known as an A-Post.

Alloy
Mixture of two or more metals

Alloy Wheels
A generic term used to describe any non-steel road wheel. The most common alloy wheels are cast aluminum. Technically, an alloy is a mixture of two or more metals. These wheels are known for their light weight and strength.

Alternating Current (AC)
Flow of electricity that periodically reverses direction

All-Wheel Drive
Often confused with Four-Wheel Drive (4WD), this drive system features four, full-time active drive wheels to reduce wheel slippage and provide greater driver control over the vehicle. All-Wheel Drive automatically splits engine torque between the front and rear wheels as needed, improving on-road traction in unfavorable road conditions. Unlike Four-Wheel Drive, All-Wheel Drive is an on-road system and is not designed for off-road use. AWD does not require the driver to actively engage the system. It is operational at all times, and requires no switches, lights or visor instructions for system operation.

Ampere
After Andre-Marie Ampere, French (1775-1836). The ampere is a unit of electrical current, or the flow of electricity.

Anti-Lock Brake System (ABS)
On a vehicle equipped with Anti-Lock Brakes, the wheels are equipped with speed sensors. When a sensor determines that a wheel is decelerating so rapidly that lockup may occur, the electro-Hydraulic Control Unit (EHCU) is activated. The EHCU then modulates the brake pressure in the appropriate brake lines by means of the solenoid-operated valves. This is intended to prevent wheel lockup and help the vehicle maintain directional stability during potentially hazardous braking situations. (See also: Rear-Wheel Anti-Lock and Four-Wheel Anti-Lock.)

Antifreeze
An additive that lowers the freezing point of a liquid

A.T.D.C
After top dead center

Automatic Locking Front Hubs
Found in some four-wheel drive vehicles, this allows the driver to engage, or "lock," the front axle hubs without leaving the vehicle.

Axle Ratio
The ratio between the rotational speed (RPM) of the drive shaft and that of the driven wheel. Gear reduction in final drive is determined by dividing the number of teeth on the ring gear by the number of teeth on the pinion gear.

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