Home → Glossary
Glossary
A
Absorption
A measure of the amount of light absorbed by an object, instead of being reflected. Dark colored and matte surfaces are least likely to reflect light (and, therefore, more likely to absorb light).
Accent Lighting
Lighting directed at a particular object in order to focus attention upon it (the illuminated object), not the light fixture itself.
ADA
Americans with Disabilities Act; ADA-compliant fixtures cannot extend more than 4” from the wall.
Ambient (General) Lighting
The soft indirect light that fills the volume of a room with illumination, softens shadows on people's faces and creates an inviting glow in the room.
Amperage
The strength of an electrical current, displayed as a measure of ampere (amp).
Ampere
A unit of current, denoting a certain amount of an electric charge passing a point in a circuit per second.
Angle of Reflectance
The angle at which a light source hits a reflective surface equals the angle at which the resulting glare is reflected back.
Architectural Lighting
Lighting that is integrated into the architecture with the sole function of providing light.
Arm
A decorative-shaped tube or casting that is used to support a socket. An arm usually has socket wires running through it.
B
Back Plate
The part of a fixture that mounts to a wall or vertical surface.
Ballast
Device that provides the proper starting and operating electrical condition to power one or more fluorescent or HID lamps. There are two types of ballasts available: magnetic and electronic.
Beam
A directed cone of light created by a directional light source.
Beam Spread
A measure of the angle of dispersion from a directional light source.
Bulb
A common consumer term for a light source, refered to as a 'lamp' in the lighting industry.
C
Candlepower
A meaurement of the intensity of light produced by a source in a specific direction.
Canopy
A decorative plate that attaches to the ceiling to cover the junction box.
CCT
Correlated Color Temperature; is a measure of how warm or cool a light source appears to the human eye, measured in degrees Kelvin. Most light sources range from 2700K-6500K, with noon daylight having a color temperature of 5000K. The higher the CCT, the cooler the light source appears, and the lower the CCT, the warmer the light source appears.
Chandelier
A multi-arm, decorative, often ornate ceiling light fixture that holds a number of bulbs.
Collection
A group of matching fixtures and/or lamps that together can bring a unified look to a home or room.
Color Temperature
See Correlated Color Temperature (CCT)
Contrast
The difference between the luminance of two surfaces (or within a surface).
CRI
Color Rendering Index; A measure from 1 to 100 of how accurately a light source renders all frequencies of its color spectrum. The higher the CRI, the better the color rendering. Incandescent lamps all have CRI 100 since all colors in their spectrum are rendered equally.
Current
The flow of electricity through a conductive surface, which is measured as Amperage.
D
Decorative Lighting
Lighting that is designed with an aesthetic (visually pleasing) attribute, in addition to providing functional illumionation.
Diffuser
A covering or shade over a light or lamp that generally softens or scatters the light and is usually used to eliminate hot spots and glare. Can be made from a variety of materials (glass, plastic, fabric, etc.) and in a variety of colors.
Dimmer
A control that regulates light levels.
Dimming Ballast
A ballast designed to allow the use of dimmers.
Driver
A device that transforms incoming household AC (alternating current) to low voltage DC (direct current). The driver also maintains constant current without fluctuations which is necessary for correct LED operation and life.
E
Efficacy
Measurement of the efficiency of a light source, based on the amount of light ouput provided in relation to how much power is consumed. Measured in lumens per watt (LPW).
Extension (ext.)
The depth of a wall light fixture (including wall brackets/sconces and vanities/bath lights). The measurement from the wall to the point of the fixtures that is farthest away from the wall.
F
Family
Same as Collection. A group of matching fixtures and/or lamps that together can bring a unified look to a home or room.
Filters
Glass or metal accessory used to alter beam patterns or introduce/change colors.
Finial
A small finishing ornament at the crown or bottom of a fixture.
Fixture
A light that is permanently attached or wired directly into a junction box. Chandeliers, bath lights and wall sconces are examples of fixtures.
Flush Mount
A decorative lighting fixture that is mounted to the ceiling and has no gap between the fixture and ceiling. A Flush Mount fixture is typically enclosed, which provides soft, even ambient lighting in the space.
Footcandle
A measurement of the intensity of light reaching a surface or point in space. Measured on the basis of lumens per square foot, one footcandle is one distributed lumen falling on one square foot of surface.
G
H
Halogen
An incandescent lamp (bulb) containing halogen gas, which recycles the tungsten, prolonging the life of the lamp, and results in a hotter and brigher burn than standard incandescent lamps.
Hard Wire
Method of fixture installation using a junction box to 'permanently' install the fixture, differing it from a portable.
HCWO
Height from Center of Wall Opening; The measurement from the top of the fixture to the center of the outlet box when installed.
HID
High Intensity Discharge; A category of lamp that emits light through electricity activating pressurized gas in a bulb. Mercury vapor, metal halide, and high pressure sodium lamps are all HID sources. They are bright and energy-efficient light sources used mainly in exterior environments.
Housing
Enclosure for recessed sockets and trim above the ceiling.
I
Incandescent
The traditional light source technology that produces light by passing a current through a filament until it glows white hot. Incandescent is the least efficient technology for producing light.
Inverted pendant
A light fixture that is suspended from the ceiling by either a chain or rod, whose shade directs light upward unlike a traditional pendant.
J
Junction Box
An enclosure that houses electrical connections, usually intended to conceal them from sight and deter tampering. Also called ‘gang boxes’ or ‘splitter boxes’.
K
Kelvin
A unit of measurement for temperature. In lighting, it is the scale by which the color temperature of a light source is defined.
L
Lamp
What the lighting industry technically calls a light bulb. A glass envelope with gas, coating, or filament that glows when electricity is applied. What everyone else calls a table or floor lamp.
Lamp Lumen Depreciation
The amount of light that would be lost at the point where the lamp has reached 50% of its rated life.
LED
Light Emitting Diode; an electronic semiconductor device that emits light when an electric current passes through it.
Line-Voltage
100-120 volt current, generally the standard in North American households.
Low-Voltage Lighting
A lighting system that utilizes a current of less than 50-volts, most commonly 12-volts, reduced from the standard American household current of 120-volt by a transformer in the power feed.
Lumen
A unit of measure of the light output emitted by a source.
Lumens per Watt
A measurement of the efficacy of a light source (bulb) given as the amount of light output by the light source in relation to how much power it consumes.
Luminaire
A complete lighting unit, including the lamps (bulbs), sockets, wiring, and the rest of the lighting fixture.
M
Milliampere
A unit of current equal to one thousandth of an ampere, abbreviated mA.
N
O
P
PAR Lamps
Lamps (bulbs) with parabolic aluminized reflectors that give exacting beam control. There are a number of beam patterns to choose from, ranging from wide flood to very narrow spot. PAR lamps can be used outdoors due to their thick glass, which holds up in severe weather conditions.
Pendant
A light fixture that is suspended from the ceiling by either a chain or rod, typically having a single shade surrounding the light source(s) that directs the light downward.
Portable
A light fixture that is free-standing and plugs into a wall outlet instead of being direct-wired, e.g. table and floor lamps.
Q
R
Rated Life
An approximate number of hours that a lamp will last, indicating when 50% of a large group of lamps have failed, when operated at nominal lamp voltage and current
Rated Lumens
A specification defining the total lumen output a light source has been tested to produce.
Reflectance
The instrinsic quality of all objects that determines how much light is reflected, instead of being absorbed. Light colored objects have high reflectance. Dark colored objects have low reflectance.
S
Sconce
A decorative lighting fixture that is mounted to the wall with typically one or two light sources. Traditionally, the light source would be a candle, which has now been replaced with electric light sources.
Semi-Flush Mount
A ceiling mounted light fixture whose main body is dropped slightly down from the ceiling, creating a gap between the fixture and ceiling.
Switch
A control to connect or disconnect an electrical device from the power source.
T
Task Lighting
Illumination designed for a work surface to provide good light, free of shadows and glare.
Timer
In lighting, a control device to turn fixtures on and off at specified times.
Torchiere
A tall floor lamp with a bowl-shaped glass that diffuses the light or directs it upward.
Transformer
In lighting, a device used in low voltage light systems to reduce electrical voltage from the standard line voltage.
U
UL
Underwriters Laboratory, an independent testing company, which tests and certifies consumer products for safety. A fixture that has been certified is often denoted as 'UL Listed.'
UPS Oversize
UPS considers a package to be oversized if the weight is greater than 150lbs, the longest side is greater than 105 inches, or if the length and girth (2x Width + 2x Height) combined is greater than 165 inches.
V
Veiling Reflection
A mirror like reflection of a bright source on a shiny surface.
Voltage
A measurement of the pressure of electricity going through a wire, measured in volts.
Voltage Drop
The decrease in voltage between the source and the load due to resistance in the wire(s).
W
Wattage
Rate of electrical power usage, measured in watts. Wattage = Voltage * Amperage
X
Xenon
An inert gas used as a component in certain incandescent lamps to produce a cooler color temperature than standard incandescent. Xenon lamps are similar to halogen but have a longer lamp life and lower pressure.