Glossary

A | B | C | D | E | F | G | H | I | K | L | M | O | P | R | S | T | U | V | W

A

A-lamp	The iconic light bulb shape most commonly associated with the traditional incandescent light bulb used throughout most homes in North America. Today, consumers can purchase energy-efficient A-lamps with LED and CFL technology. Also called A-shaped bulbs.
Accent lighting	Technique that emphasizes a particular object or draws attention to a particular area, using tight beam control. Also called highlighting.
Accent fixture	Type of fixture that provides focused, directional lighting to call attention to an object or an area within a space. Includes ceiling-mounted track and recessed accent fixtures.
Adjustable head	Adjustable fixture that is surface-mounted, or that inserts into a linear track and provides directional lighting.
Ambient lighting	Lighting that provides a uniform light level throughout an area. Also called general lighting.
Annual energy savings	Difference per year of energy (measured in kilowatt-hours) when upgrading to improved lighting.
Annual energy use	Energy (measured in kilowatt-hours) used for lighting. Determined by fixture quantity, power demand, and hours of use.
Annual bulb replacement costs	Average cost per year of replacement bulbs, excluding labor. Some bulbs are expected to last several years, so this amount could be less than the price of one bulb.
Annual operating cost savings	Average savings per year from reduced electricity and bulb replacement costs achieved with improved lighting.
Annual operating cost	Annual energy cost plus annual bulb replacement costs.
Aperture	An opening, usually in a recessed fixture, through which light enters a space.
Architecturally integrated lighting	Lighting integrated into the structure of the room, mounted horizontally on a wall or ceiling with a shield to hide bulb(s) from view. Includes cove, soffit, and valance fixtures.
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B

Baffle	Opaque or translucent element that shields a light source from direct view at certain angles or that absorbs unwanted light.
Ballast	Device used with a fluorescent light source to provide the necessary circuit conditions (voltage, current, and wave form) for starting and operation.
Bi-pin base	Base with two pins used for some tungsten-halogen reflector bulbs, low-voltage tungsten-halogen bulbs, and fluorescent lamps.
BR-lamp	Bulged reflector, a common reflector bulb that provides a wide, soft beam.
Bulb	Manufactured light source, such as incandescent, CFL, and LED bulbs. Bulbs are sometimes called lamps, such as an A-lamp or fluorescent lamp (tube).
Bulb life	See lamp life.
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C

Candelabra bulb	Decorative bulb shaped like a flame. Also called candle bulb.
Capsule CFL	CFL covered by a diffusing bulb, typically made of glass or polymer.
Ceiling-mounted diffuser	Fixture mounted directly on the ceiling, as opposed to a recessed or suspended fixture.
Center beam candlepower (CBCP)	Luminous intensity (in candelas) of a reflector bulb measured at the center of its beam.
CFL	See compact fluorescent lamp.
Circline lamp	Fluorescent lamp (tube) bent in a circle so that the ends meet at the socket.
Color	Color appearance of a light source, and how it makes other colors appear. See correlated color temperature and color rendering index.
Color rendering index (CRI)	Rating system for light sources describing color appearance of objects being illuminated, ranging from 0-100. Lower CRI indicates that some colors may appear unnatural when illuminated by the bulb. CRI of two or more bulbs should only be compared if bulbs have same correlated color temperature.
Compact fluorescent lamp (CFL)	Small fluorescent bulb, usually with one or more bends in the tube.
Contrast	Relative brightness (luminance) of an object against its immediate background.
Control	Mechanism to turn bulbs on and off, or dim bulbs, including switches, dimmers, timers, and sensors.
Correlated color temperature (CCT)	Rating system for light sources that describes the color appearance ("warmth" or "coolness") of the light. Low color temperature (2700-3000K) looks yellowish white. High color temperature (4100K+) looks bluish-white. CCT is listed on bulb packaging in North America.
Cove	Architecturally integrated lighting that directs light upward.
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D

Daylight	Light from the sun.
Diffuse lighting	Light that does not come from any particular direction. Diffuse lighting produces less-distinct shadows than directional lighting.
Dimmer	Device used to control intensity of light emitted by a fixture.
Direct glare	Glare resulting from very bright sources of light in the field of view. It is usually associated with bright light from fixtures and windows. A direct glare source may also affect performance by reducing the apparent contrast of objects in the field of view, especially those near the source of light.
Directional lighting	Lighting produced by fixtures that distribute all, or nearly all, of the light in one direction.
Downlight	Directional fixture that directs all light downward.
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E

Efficacy (of a light source)	Total light output of a light source divided by the total power input, in lumens per watt. Higher efficacy is usually better for reducing power use and improving energy efficiency.
Efficiency (of a fixture)	The ratio of light (lumens) emitted by a fixture to that emitted by the bare bulb(s) in percent. A measurement of how much light is not blocked by the fixture. The trade-off for fixture efficiency is glare control.
Electronic ballast	Ballast that uses electronic circuitry to provide the voltage and current needed to start fluorescent bulb(s) and maintain operation. Electronic ballasts weigh less than magnetic ballasts and operate more quietly and efficiently. Electronic ballasts operate bulbs at a higher frequency than magnetic ballasts (20,000-60,000 Hz compared to 60 Hz), which eliminates flicker and increases efficacy. See also ballast.
Energy	Measured in watt-hours, the product of power (watts) and time (hours). Energy used for lighting can be saved either by reducing the amount of power required or by reducing the amount of time lighting is used.
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F

Fixture	Complete lighting unit consisting of a bulb or bulbs, together with the parts designed to distribute the light, to position and protect the bulbs, and to connect the bulbs to the power supply. Also called luminaire.
Flood bulb	Bulb that produces a relatively wide beam of light.
Fluorescent light	See linear fluorescent lamp or compact fluorescent lamp.
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G

G-lamp	Globe-shaped, spherical bulb.
General lighting	See ambient lighting.
Glare	Discomfort and/or loss of visibility associated with bright light within the field of view. See also direct glare and reflected glare.
Globe	Spherical transparent or diffusing enclosure intended to protect a bulb, diffuse its light, or change the light color.
GU24 base	Pin base for self-ballasted bulbs, typically CFLs. Commonly used in ENERGY STAR® fixtures.
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H

Halogen incandescent bulb	Incandescent bulb with an encapsulated filament containing halogen gas and higher efficacy than common incandescent bulbs. Sometimes called quartz bulbs because the capsule is made from quartz glass.
Halogen IR-lamp	Halogen bulb with an infrared-reflecting coating on the capsule surrounding the filament to increase efficacy.
Highlighting	See accent lighting.
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I

Illuminance	Amount of light falling on a surface, measured in footcandles or lux.
Incandescent bulb	Produces light by electrical resistance heating of a filament. For many years, the incandescent light bulb has been the most popular bulb used in homes in North America. Today, CFL and LED bulbs have been developed to replace this technology.
Incremental cost	Difference between the cost of two items that perform similar functions.
Indirect lighting	Light arriving at a point or surface after reflection from one or more surfaces (usually walls and/or ceilings) that are not part of the fixture.
Initial cost	Original cost of equipment, bulbs, and installation, exclusive of operating costs such as energy, maintenance, and bulb replacement.
Input power	Active power used by a bulb or fixture, measured in watts.
Interval timer	Lighting control that automatically switches the fixture off after a selected time interval. An interval timer can be either electronic or mechanical.
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K

Kilowatt (kW)	1000 watts. See also watt.
Kilowatt-hour (kWh)	Measure of electrical energy consumed; 1 kilowatt-hour is equal to 1000 watts used for 1 hour. See also watt and watt-hour.
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L

Lamp	In common parlance, a lamp is a plug-in fixture, such as a desk, floor, or table lamp. Within the lighting profession, a lamp is a light bulb, such as an A-lamp or fluorescent lamp (tube).
Lamp life	Number of hours when half of a large group of bulbs are expected to have failed; actual lamp life may be shorter or longer than number shown on bulb packaging. Lamp life does not necessarily constitute a manufacturer warranty. Failure is defined differently for LEDs than other light sources.
LED	See light-emitting diode.
Light	Radiant energy that is capable of producing a visual sensation. The visible portion of the electromagnetic spectrum extends from about 380 to 770 nanometers.
Light distribution	Pattern of light that is produced by a light source or fixture, or patterns of light created in a room.
Light-emitting diode (LED)	Semiconductor diode that radiates in the visible region of the electromagnetic spectrum.
Light output	Luminous flux, measured in lumens. This is listed on bulb packaging in North America. See also lumen.
Light source	An object that produces light, such as a light bulb or the sun.
Lighting technique	A way to light a space to achieve a desired effect.
Linear fluorescent lamp (tube)	Straight, tubular fluorescent lamp. Also called linear fluorescent bulbs or tubes.
Louver	Series of baffles or reflectors used to shield a light source from view at certain angles, absorb unwanted light, or reflect light.
Lumen	Measurement unit of light output (luminous flux), the time rate of flow of light.
Lumens per watt (LPW)	See efficacy.
Luminaire	See fixture.
Luminance	Closely related to the "brightness" of an object, the luminous intensity of a surface of a given projected area. Measured in candelas/m2.
Luminous flux	The time rate of flow of light, measured in lumens.
Lux	Standard international unit of illuminance equal to 1 lumen per square meter. One lux equals 0.0929 footcandles.
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M

Magnetic ballast	Ballast with a magnetic core and coil to provide the voltage and current needed to start a fluorescent bulb and to maintain its operation. Magnetic ballasts are heavier and less efficient than electronic ballasts. See also ballast.
Matte surface	Surface from which the reflection is predominantly diffuse.
Motion sensor	See sensor.
Mounting height	Distance from the floor to the center of the fixture or to the plane of the ceiling for recessed equipment.
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O

Occupancy sensor	See sensor.
Operating cost	See annual operating cost.
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P

PAR-lamp	Parabolic aluminized reflector (PAR) bulb. Hard glass bulb and an interior reflecting surface with controlled beam spread. A number after PAR, such as in "PAR30", indicates the width of the bulb.
Pattern	Lighting design showing how lighting in commonly used rooms can be more energy efficient, or can improve visibility or appearance of the space.
Pendant fixture	See suspended fixture.
Photosensor	See sensor.
Power reduction factor	In energy calculations, this term accounts for power reduction when taking advantage of lighting controls.
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R

Rated life	See lamp life.
Recessed fixture	Fixture mounted above the ceiling (or behind a wall or other surface) with the opening of the fixture flush with the surface.
Reflected glare	Glare resulting from bright reflections from polished or glossy surfaces in the field of view. Reflected glare usually is associated with reflections from within a visual task or areas in close proximity to the region being viewed.
Reflector	Surface of mirrored glass, painted metal, polished metal, or metalized plastic that is shaped to project the beam from a light source in a particular direction. Reflectors may be an integral part of a bulb or they may be part of the fixture.
Reflector bulb	Class of bulb with reflecting material integrated into the bulb to direct the light, such as bulged reflector (BR), parabolic aluminized reflector (PAR), and multi-faceted reflector (MR) bulbs. LED versions of these bulbs can achieve the same optical properties without using reflector materials.
Relamp	To replace a light bulb.
Rewire	To change a light fixture at an existing electrical junction box.
Remodel	To install new wiring and fixtures.
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S

Sconce	A decorative and/or functional wall-mounted fixture, usually non-linear.
Screwbase CFL	Compact fluorescent lamp (CFL) with a medium screwbase that fits into a standard incandescent bulb socket.
Sensor	Sensors for indoor use include vacancy sensors (manual on/auto off) and occupancy sensors (auto on/off). Sensors for outdoor use include motion sensors (auto on/off) and dusk-to-dawn sensors (auto on/off). Vacancy, occupancy, and motion sensors either respond to a change in infrared heat motion, or a change in ultrasonic frequency. Dusk-to-dawn sensors, also known as photosensors, turn on automatically when light drops below a specified level.
Shade	Device on a fixture used to prevent glare (by hiding the light source from direct view), control light distribution, and sometimes diffuse (and perhaps color) the light emitted.
Simple payback	The time (in years) required to save enough in operating costs to pay back the incremental capital cost of improved lighting. This is not a net present value calculation and does not take into account interest or other financial considerations.
Soffit	Architecturally integrated lighting that directs light downward from the cornice or soffit between the wall and ceiling to light the wall surface below.
Spot bulb	Bulb that provides a relatively narrow beam of light.
Surface-mounted fixture	Light fixture mounted directly to a wall or ceiling. See ceiling-mounted diffuser.
Suspended fixture	Fixture hung from a ceiling. Also called a pendant.
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T

Task lighting	Lighting directed to a specific surface or area to provide illumination for visual tasks.
Three-way bulb	Bulb that can provide low, medium, and high light output. A special socket is required to use the three levels of this bulb. Used in some table lamps and other plug-in fixtures. Also called a three-level bulb.
Timer	See interval timer.
Torchiere	Floor-standing light fixture that directs all or nearly all of the light upward for indirect lighting.
Track head	Adjustable fixture that connects to the track in a track lighting system. See track lighting.
Track lighting	A lighting system with an electrically fed linear track that accepts one or more track heads. The track heads can be easily relocated along the track.
Trim	Baffles, cones, rims, and other treatments for apertures of downlights. Trim is usually the part of the fixture that is visible from below the ceiling.
Troffer	Recessed fixture with an opening flush with the ceiling. Typically rectangular or square in shape, as in a 2-foot by 4-foot fixture.
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U

Under-cabinet lighting	Fixtures mounted on the underside of cabinets to provide task lighting, typically in a kitchen.
Uplight	Fixture that directs the light upward onto the ceiling and upper walls of a room.
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V

Valance	Architecturally integrated lighting that directs light both up and down a wall.
Vanity light	Wall-mounted fixture located near a bathroom mirror.
Voltage (V)	Wall-mounted fixture located near a bathroom mirror.
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W

Wall washing	Technique that evenly lights a wall from top to bottom without spilling light away from the wall into the room.
Watt (W)	Unit of active electric power; the rate at which electric energy is used.
Watt-hour	Unit of electric energy. One watt-hour is the amount of energy consumed at the rate of 1 watt during a 1-hour period.
Wattage	Active electrical power consumed by a device.
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