Lighting Definitions

Amperes
("Amps.") A measure of electrical current. In incandescent lamps, the current is related to voltage and power as follows: Watts (power) = Volts x Amps (current).
ANSI (American National Standards Institute)
A consensus-based organization which coordinates voluntary standards for the physical, electrical and performance characteristics of lamps, ballasts, luminaires and other lighting and electrical equipment.
ANSI Codes
These are 3-letter codes assigned by the American National Standards Institute. They provide a system of assuring mechanical and electrical interchangeability among similarly coded lamps from various manufacturers.
Arc
A general term for a high intensity electrical discharge occurring between two electrodes in a gaseous medium, usually accompanied by the generation of heat and the emission of light.
Arc Length
In High Intensity Discharge lamps this is the distance between the electrode tips, which represents the physical length of the electrical discharge.
Average Life (Rated Lamp Life)
This is the manufacturer provided rating for the average expected life of a lamp. 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.
Base Type
The base is the end of the lamp that fits into the receptacle connected to the electrical supply. There are many types of bases used in lamps, screw bases being the most common for incandescent and HID lamps, while bipin bases are common for linear fluorescent lamps.
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 Spread
The angular dimension of the cone of light from reflectorized lamps encompassing the central part of the beam out to the angle where the intensity is 50% of maximum. The beam angle sometimes called "beam spread" is often part of the ordering code for the reflectorized lamps.
Bi-Pin
Any base with two metal pins for electrical contact. This is the typical base for a fluorescent tube of 1 to 4 feet in length. It consists of 2 prong contacts which connect into the fixture. Medium bi-pins are used with type T8 and T12 tubular fluorescent lamps, and miniature bi-pins are used for tubular T5 fluorescent lamps.
Black Light
A popular term referring to a light source emitting mostly near UV (320 to 400 nm) and very little visible light.
Bulb Type
The bulb type refers to the shape and class of the bulb.
Candle Power (Candela)
The measure of luminous intensity of a source in a given direction. The term has been retained from the early days of lighting when a standard candle of a fixed size and composition was defined as producing one candela in every direction. A plot of intensity versus direction is called a candela distribution curve and is often provided for reflectorized lamps and for luminaires with a lamp operating in them.
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
number indicating the degree of "yellowness" or "blueness" of a white light source. Measured in kelvins, Color Temperature represents the temperature an incandescent object (like a filament) must reach to mimic the color of the lamp. 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.
Cool White
A term loosely used to denote a color temperature of around 4100 K. The Cool White (CW) designation is used specifically for T12 and other fluorescent lamps using halophosphors and having a CRI of 62.
Daylight Lamp
A lamp resembling the color of daylight, typically with a color temperature of 5500 K to 6500K
Dichroic Reflector (or Filter)
A reflector (or filter) that reflects one region of the spectrum while allowing the other region(s) to pass through. A reflector lamp with a dichroic reflector will have a "cool beam" i.e. most of the heat has been removed from the beam by allowing it to pass through the reflector while the light has been reflected.
Dimmable
Whether or not the lamp lumens can be varied while maintaining reliability.
Filament
Filaments are designated by a letter combination in which C is a coiled wire filament, and CC is a coiled wire that is itself wound into a larger coil. Numbers represent the type of filament-support arrangement.
Finish
The bulb coating of the bulb. Typical values include clear, frost, and colored.
Flood
Used to refer to the beam pattern of a reflector lamp, which disperses the light over a wide beam angle, typically 20 degrees or more. ("Flood" as opposed to "spot")
Full Spectrum Lighting
A marketing term, typically associated with light sources that are similar to some forms of natural daylight (5000K and above, 90+ CRI), but sometimes more broadly used for lamps that have a smooth and continuous color spectrum.
Halogen Lamp
A halogen lamp is an incandescent lamp with a filament that is surrounded by halogen gases, such as iodine or bromine. Halogen gases allow the filaments to be operated at higher temperatures and higher efficacies. The halogen participates in a tungsten transport cycle, returning tungsten to the filament and prolonging lamp life.
Halogen-IR (HIR) Lamp
GE designation for high-efficiency tungsten halogen lamps. HIR lamps utilize shaped filament tubes coated with numerous layers of materials that transmit light but reflect the heat (infrared) back into the filament. This reduces the power needed to keep the filament hot.
High Intensity Discharge (HID) Lamp
A general term for mercury, metal halide and high-pressure sodium lamps. HID lamps contain compact arc tubes which enclose various gases and metal salts operating at relatively high pressures and temperatures.
High-Pressure Sodium (HPS) Lamp
HPS lamps are high intensity discharge light sources that product light by an electrical discharge though sodium vapor operating at relatively high pressures and temperatures.
Hot Restart Time
Time it takes for a High Intensity Discharge lamp to reach 90% of light output after going from on to off to on.
Kelvin
A unit of temperature starting from absolute zero, parallel to the Celsius (or Centigrade) scale. 0C is 273K.
Light Center Length (L.C.L.)
The distance between the center of the filament, or arc tube, and a reference plane - usually the bottom of the lamp base.
Lighting Industry Federation (LIF) Code
Codes that are assigned by the Lighting Federation of London U.K. They ensure electrical and mechanical interchangeability of similarly coded lamps. LIF codes are divided into groups according to the primary application of the lamps.
Lumens
A measure of the luminous flux or quantity of light emitted by a source. For example, a dinner candle provides about 12 lumens. A 60-watt Soft White incandescent lamp provides about 840 lumens.
Maximum Overall Length (M.O.L.)
The end-to-end measurement of a lamp including the base, expressed in inches or millimeters.
Medium Base
Usually refers to the screw base typically used in household incandescent lamps. There is also the medium bipin base commonly used in T12 and T8 fluorescent lamps.
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.
Mogul Base
A screw base used on larger lamps, e.g. many HID lamps.
MR-16 and MR-11
A line of low voltage compact reflector lamps used for accent and spot lighting. The 16 and 11 refer to 16 eighths of an inch diameter and 11 eighths.
Orientation (also Operating Position or Burn Position)
Mercury and High Pressure Sodium lamps may be operated in any burn position and will still maintain their rated performance specifications. Metal Halide and Low Pressure Sodium lamps, however, are optimized for performance in specific burn positions, or may be restricted to certain burn positions for safety reasons.

Any, Universal = Universal burning position
BD = Base Down
BD30 = Within 30° of Vertical Base Down
BD45 = Within 45° of Vertical Base Down
BDTH = Base Down to Horizontal
BU = Base Up
BU ±15° = Base Up Within ±15°
BU30 = Within 30° of Vertical Base Up
HD = Horizontal Down
Horiz ±10° = Within ±10° of Horizontal Position
Horiz ±15° = Within ±15° of Horizontal Position
Horiz ±30° = Within ±30° of Horizontal Position
Horiz ±4° = Within ±4° of Horizontal Position
Horiz ±40° = Within ±40° of Horizontal Position
Horiz ±45° = Within ±45° of Horizontal Position
Horiz ±60° = Within ±60° of Horizontal Position
Horiz ±75° = Within 75° of Horizontal Position
Horizontal = Horizontal
p20 = Within ±20° of Horizontal Position
p90/15 = Horizontal Down
s30 = Within ±30° of Vertical Position
s30 p20 = Within ±30° of Vertical Position, or Within ±20° Horizontal Position
s45, anode down = Within ±45° of Vertical Position, Anode Down
s90 = Within ±90° of Vertical Position
VBD = Vertical Base Down
VBU = Vertical Base Up
Vert ±10° = Within ±10° of Vertical Position
Vert ±15° = Within ±15° of Vertical Position
Vert ±30° = Within ±30° of Vertical Position
Vert ±4° = Within ±4° of Vertical Position
Vert ±45° = Within ±45° of Vertical Position
Vert ±5° = Within ±5° of Vertical Position
Vert ±90° = Within ±90° of Vertical Position
Order Code
General short lamp description by wich a lamp is often refered to. It is common to include watt and volt information in the order code. A lamp may have multiple order codes.
PAR Lamp
PAR is an acronym for parabolic aluminized reflector. A PAR lamp, which may utilize either an incandescent filament, a halogen filament tube or a HID arc tube, is a precision pressed-glass reflector lamp. PAR lamps rely on both the internal reflector and prisms in the lens for control of the light beam.
Product Code
The product code for a lamp is the manufacturer assigned product code for that item.
Quartz
A name for fused silica or melted sand from which many high-temperature containers are fashioned in the lighting industry. Quartz looks like glass but can withstand the high temperatures needed to contain high intensity arc discharges.
Spot
A colloquial term referring to a reflector lamp with a tight beam of light, typically around 10 degrees or less. It comes from the fact that such a lamp produces a narrow spot of light as opposed to a wide flood of light.
Volt
A measure of "electrical pressure" between two points. The higher the voltage, the more current will be pushed through a resistor connected across the points. The volt specification of an incandescent lamp is the electrical "pressure" required to drive it at its designed point. The "voltage" of a ballast (e.g. 277 V) refers to the line voltage it must be connected to.
Warm White
Refers to a color temperature around 3000K, providing a yellowish-white light.
Watt
A unit of electrical power. Lamps are rated in watts to indicate the rate at which they consume energy.