Designations for lamps established by the American National Standards Institute. ANSI also develops consensus standards for lamps, ballasts, and test procedures.

The opening of a fixture through which light exits.

A general reference to built-in lighting, such as recessed downlights, cove, and valences.

A clock programmed according to sunrise and sunset (seasonal) rather than 24-hour time. Used for timing controls.

The number of hours required for half of a large group of lamps to fail or burn out. The actual life of any lamp or small group of lamps is typically different from the average rated life.

Fixture or electrical enclosure installed during the Rough-In phase of the project.

Part of the fixture that blocks light to prevent glare and control brightness. Often painted black to absorb light.

Electrical or electronic component required for fluorescent and HID lamps. They provide enough voltage to start the lamp and limit the current for continuing operation.

The fixture used at a mirror or over a vanity. Ideally a long, well-diffused light source.