Accent lighting

Directional lighting to emphasize a particular object or draw attention to a display item.


The process by which the human eye adjusts to a change in light level.

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).


An alloy of mercury which is an upgrade from traditional liquid mercury. Since it gives better mercury vapor control in the glass envelope the lamps that use amalgam perform better over a wider variety of temperatures and operating positions.


The "positive" terminal of a diode.


An inert gas used in incandescent and fluorescent lamps. In incandescent lamps argon retards the evaporation of the filament and, thereby, lengthens the average rated life of the lamp.




 An electrical device used with fluorescent lamps to supply sufficient voltage to start and operate the lamp but then limit the current during operation.

Ballast Factor (BF)

 This is the percentage of a lamp's rated lumen output that can be expected when operated on a specific, commercially available ballast. For example, a ballast with a ballast factor of 0.93 will result in the lamp's emitting 93% of its rated lumen output. A ballast with a lower BF results in less light output and also generally consumes less power.


 A loose way of referring to a lamp. "Bulb" refers to the outer glass bulb containing the light source.




 A very small square of semi-conducting material. Also known as a "die," it is the "active" light-emitting component of an LED.

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. Measured in kelvins, CCT 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




A transparent or translucent piece of glass, silicone, or plastic designed to control light by scattering or diffusing it in order to create softer light without much glare.



Any lighting product (light fixture or light bulb) that is designated as dimmable can be dimmed if the correct dimming device (such as a dimmer) is used to decrease or increase the amount of light that light fixture gives off.

Discharge Tube

A tube (usually made of glass) that contains gas or a metal vapor that ionizes when voltage is applied, resulting in the emission of light. Many different gases are used in discharge tubes, including xenon, neon, argon, mercury, and sodium.

Double-ended Lamp

A lamp that has 2 bases or points of electrical and physical connection that provide extra stability in rough service applications.


A small light fixture recessed into the ceiling that usually concentrates the light in a downward

Driver, LED

An electronic device that acts as the power supply for LEDs. A driver regulates the current in order to maintain steady lumen output and prevent variation.



A measurement of efficiency used to compare light output to energy consumption. Efficacy is measured in lumens per watt (similar to miles/gallon for a motor vehicle). A 100-watt light source that produces 1750 lumens of light has an efficacy of 17.5 lumens per watt (L/W).

Electronic Ballast

A type of ballastt with electronic components that increases the standard operating frequency of electricity from 60 cycles per second (the U.S. standard) to 20 kHz (20,000 cycles/second) or higher. This increase in operating frequency is important for greatly reducing the strobscopic effect or flickering that is associated with fluorescent lamps. Electronic ballasts are an improvement over magnetic ballasts because they are quieter, lighter in weight, and more efficient in converting electrical energy into light energy while producing less heat.



A tungsten wire that incandesces or lights up when an electric current passes through it.

Fluorescent Lamp

A low-pressure mercury electric-discharge lamp (light bulb) in which a phosphor coating on the inside of the glass tubing transforms some of the ultraviolet energy created inside the lamp into visible light.



The technique of installing two or more on/off switches, dimmers or electrical recetacles side by side in one wall junction box.


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.

Hertz (Hz)

The standard unit of measurement for frequency (how many times something occurs in a unit of time), usually how many cycles occur in 1 second. Named after German physicist, Heinrich Hertz, the unit was first established in 1930. In lighting, Hz is the unit used to measure  altemating current .


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.


Kilowatt (kw)

A measure of electrical power equal to 1000  watts.

A unit of temperature starting from absolute zero, parallel to the Celsius (or Centigrade) scale. 0C is 273K


Lamp Types
Filament lamps: Incandescent, Halogen, Halogen-IR. 
Discharge Lamps: Fluorescent, HID (High Intensity Discharge) 
HID Lamps: Mercury, HPS (High Pressure Sodium), MH (Metal Halide) and CMH (Ceramic Metal Halide)

A transparent or semi-transparent element which controls the distribution of light by redirecting individual rays. Luminaires often have lenses in addition to reflectors.

Light Emitting Diode

Light emitting diode. A small electronic device that lights up when electricity is passed through it. LEDs are quite energy-efficient and have very long lives. They can be red, green, blue or white in color.

Light Fixture

A complete lighting unit consisting of a lamp (light bulb) or lamps, a housing, a connection to an external source of electrical power, and sometimes a transformer, ballast, or driver that modifies the incoming power to meet the unique electrical needs of the lamp(s) being used.

Light Pollution

Any adverse effect of artificial light.

Light Quality

A measurement of a person’s comfort and perception based on the lighting.


An international unit (SI) of measurement used to describe the amount of light that a light source  produces or emits.


A light fixture. This should not be confused with the term, luminary, which is a small open paper bag, sometimes with a design on it, containing a lit votive candle set in sand. Luminaries are often used to line outdoor walkways to provide a festive mood to a setting and a certain level of safety. In Mexico and the southwest USA, the terms, luminary and luminaries, become luminaria and luminarias. The term, luminary, can also refer to a person who has attained eminence in his/her field or is an inspiration to others.

Luminaire Efficiency

The ratio of lumens emitted by a light fixture to the lumens emitted by the lamp(s) installed in that fixture. A luminaire  with 0.8 efficiency is considered high whereas an efficiency of 0.6 is considered standard.


One lumen per square meter. Unit of illuminance.



A chemical element found in nature that is added to the inside of fluorescent (including CFLs ), metal halide , and high pressure sodium light bulbs during their manufacturing process. It is a silvery-looking liquid metal at room temperature that is a neurotoxin; that is, a toxic substance that can attack the nervous system and brains of humans.

MR16 Lamp

A halogen multi-faceted reflector lamp that measures 16/8 inches in diameter and which directs a sharp, well-defined beam of light.



The coating on the inside glass tubing of a fluorescnet lamp  that transforms some of the ultraviolet  energy created inside the lamp into visible light.

Power Factor

A ratio that indicates if the voltage  and current are out of phase in an electrical circuit. A power factor that is near 1.0 is considered good because this means that the electrical circuit is able to do work efficiently. The closer the power factor is to 0, the more inefficient the electrical circuit is. A high power factor (HPF) is generally considered to be 0.90 and above and a normal power factor (NPF) is generally considered to be between 0.5 and 0.6.



The standard unit of electrical force or pressure between two points in an electric circuit. The greater the voltage, the faster electrons will travel through a circuit, meaning the greater the current running through a circuit. The unit is named after Alessandro Volta, an Italian physicist who made the first electric cell


Wall Grazing

A lighting term that refers to the dramatic highlight and shadow effects on uneven surfaces such as draperies, stone, and brick. Grazing creates easily distinguishable high and low levels of light on the irregular surface.

 Watt (W)

The unit for measuring power. In physics terms, one watt is one Joule of energy transferred or dissipated in one second. Electrical power is calculated as: Watts = Volts x Amps x Power Factor.