Amperes
("Amps.") A measure of electrical current. In incandescent lamps, the current is related to voltage and power as follows: Current (Amps) = Power (Watts) / Voltage (Volts).

Bayonet
A style of bulb base which uses keyways instead of threads to connect the bulb to the fixture base. The bulb is locked in place by pushing it down and turning it clockwise.

Beam Angle
Also known as 'beam spread', this is the angular dimension of the cone of light from reflectorized lamps, (such as R and PAR types) encompassing the central part of the beam out to the angle where the intensity is 50% of maximum.

Bi-Pin
This is a low voltage lamp without a reflector. It has a 2-pin base and is available in a variety of wattages.

Ceramic Metal Halide (CMH®)
A type of metal halide lamp that uses a ceramic material for the arc tube instead of glass quartz, resulting in better color rendering (>80 CRI) and improved lumen maintenance.

Color Rendering Index (CRI)
An international system used to rate a lamp's ability to render object colors. The higher the CRI (based upon a 0-100 scale) the richer colors generally appear. CRI ratings of various lamps may be compared, but a numerical comparison is only valid if the lamps are close in color temperature. CRI differences among lamps are not usually significant (visible to the eye) unless the difference is more than 3-5 points.

Color Temperature (Correlated Color Temperature - CCT)
A number indicating the degree of "yellowness" or "blueness" of a white light source. Yellowish-white ("warm") sources, like incandescent lamps, have lower color temperatures in the 2700K-3000K range; white and bluish-white ("cool") sources, such as cool white (4100K) and natural daylight (6000K), have higher color temperatures. The higher the color temperature the whiter, or bluer, the light will be.

Compact Fluorescent Lamp (PLC or CFL)
The general term applied to fluorescent lamps that are single-ended and that have smaller diameter tubes that are bent to form a compact shape. These are available in ES and BC bases.

Fluorescent Lamp
An energy efficient lamp which utilizes an electric discharge through low pressure mercury vapor to produce ultra-violet (UV) energy. These are available in a range of sizes and styles, and produce different kinds of light.

Halogen Lamp
A halogen lamp is an incandescent lamp with a filament that is surrounded by halogen gases, such as iodine or bromine. They generally have a long lamp life and can be either tubular or low voltage lamps.

Incandescent Lamp
A light source that generates light utilizing a thin filament wire (usually of tungsten) heated to white heat by an electric current passing through it.

Lamp
The term used to refer to the complete light source package, including the inner parts as well a the outer bulb or tube. "Lamp", of course, is also commonly used to refer to a type of small light fixture such as a table lamp.

Light
Radiant energy that can be sensed or seen by the human eye. Visible light is measured in lumens.

Lux (lx)
A unit of illuminance or light falling onto a surface. One lux is equal to one lumen per square meter. Ten lux approximately equals one footcandle.

Mercury Lamp
A high-intensity discharge light source operating at a relatively high pressure (about 1 atmosphere) and temperature in which most of the light is produced by radiation from excited mercury vapor. Phosphor coatings on some lamp types add additional light and improve color rendering.

Metal Halide Lamp
A high-intensity discharge light source in which the light is produced by the radiation from mercury, plus halides of metals such as sodium, scandium, indium and dysprosium. Some lamp types may also utilize phosphor coatings.

Rated Lamp Life
For most lamp types, rated lamp life is the length of time of a statistically large sample between first use and the point when 50% of the lamps have died. It is possible to define "useful life" of a lamp based on practical considerations involving lumen depreciation and color shift.

Voltage
A measurement of the electromotive force in an electrical circuit or device expressed in volts. Mains voltage in Australia is 240volts, and low voltage is generally 12volts. Other variations are possible.

Watt
A unit of electrical power. Lamps are rated in watts to indicate the rate at which they consume energy.