Lighting Glossary

Lighting Glossary

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A Lamp - General service incandescent lamp with a medium base or Edison base.

AC (Alternating Current) - Current that flows in one direction and then alternates its flow in the other direction.

Accent Lighting - Directional lighting, such as track lighting and recessed downlights, that draws attention to a displayed object or surface, or to highlight, dramatize, and focus attention on a defined space.

ALA (The American Lighting Association) - The trade organization of the residential lighting industry in the U.S., Canada and the Caribbean, with members that are lighting manufacturers, showrooms, independent manufacturers' sales representatives, designers and other industry associates who promote the sale and proper use of quality lighting products in the home.

Alzak - A trade name for a method of anodizing, now a generic term for brightened, anodized aluminum, a finish with a brushed nickel appearance developed by Alcoa Aluminum as a bright, shiny coating.

Ambient Lighting - General lighting for any interior environment, in contrast to directional lighting.

Amperes (Amps) - A measure or intensity of electrical current. In incandescent lamps, the current is related to voltage and power as follows: Watts (power) = Volts x Amps (current).

Anodized - A highly durable finish consisting of a thin, near transparent coating of aluminum oxide on the surface of an aluminum reflector.

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 Ballast - Ballast type used to operate lamps in accordance with ANSI standards.

Antique Finish - A finish that simulates aging, often accompanied with a dark pigment paint wiped across a metal part.

Application (lighting application) - The particular use of the lamp or lighting fixture (such as a high-bay industrial application or a retail lighting application) including specific parameters and usage of light sources.

Auto Rest Shutdown Circuit - A circuit that senses lamp end life and will automatically shut off power to the lamp(s). When a new lamp is inserted in the socket, the ballast resets, and turns on the lamp automatically. Some shutdown circuits require the power to be interrupted before a new lamp will re-light.


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Back Light - Illumination from behind an object that creates a silhouette or a dramatic outline, creating separation between the subject and its background.

Baffle - Fixture component, an opaque or translucent element, that blocks light to prevent glare and control brightness, or to reflect and redirect light.

Ballast - Device required for fluorescent and HID lamps that provides enough voltage to control start up and operation of the electric discharge lamp, and then limit current for continuing operation.

Ballast Factor (BF) - The fractional flux of a fluorescent lamp operated on a ballast compared to the flux when operated on the standard ballast specified for rating lamp lumens.

Base or Socket- The socket is the receptacle connected to the electrical supply; the base is the end of the lamp that fits into the socket. Screw bases are the most common for incandescent and HID lamps, while bi-pin bases are common for linear fluorescents.

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 - The key element of a directional light, accent light, or downlight.

Beam Angle - The angle between the two directions for which the intensity is 50% of the maximum intensity in a plane through the nominal beam centerline.

Beam Spread - Width of the beam in degrees, defined as the point where intensity falls to 50% of maximum candlepower. For most PAR and MR lamps, this is the apex angle. For asymmetrical beams, this is expressed as length x width. Most reflector halogen bulbs are offered in varying degrees.

Beveled Glass - Clear glass with edges cut to add depth and a special effect.

Binning - A process by which LEDs are sorted in order to maintain proper color consistency between individual LEDs.

Bullet - An accent light, sometimes with a round back, used to create dramatic light in a small space.

Bi-Pin - Any base with two metal pins for electrical contact, including a variety of halogen lamps, as well as T-8 and T-12 tubular fluorescent lamps, and miniature bi-pins are used for tubular T-5 fluorescent lamps.

BR Lamp - Bulged reflector modified R lamp, that is usually an incandescent, to meet EPACT standards and produce a soft-edged beam that is less precise and narrower than PAR lamps.

Bulb - Bulb refers to a lamp or the outer glass bulb containing the light source.

Bulb Size - Bulb shape followed by its size (the maximum diameter of the bulb expressed in eighths of an inch). The code includes a reference such as T4 to represent the size of the tube.

Button Light - WAC Lighting's versatile luminaire that is available with LEDS, as well as xenon and halogen lamping, and can be surface mounted or recessed for a built in look for under cabinet and other hard to light applications.


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Can - Term for a recessed downlight housing.

Canadian Standards Association (CSA) - An organization that writes standards and tests lighting equipment for performance, as well as electrical and fire safety. Canadian provincial laws generally require that all consumer products in Canada must have CSA or equivalent approval.

Candela (cd) - The measure of luminous intensity of a source in a given direction, a term retained from the early days when a standard candle of a fixed size and composition was defined as producing one candela in every direction. The SI unit of luminous intensity, equal to one lumen per steradian.

Candlepower - Luminous intensity expressed in candelas, in a particular direction.

Canopy - Fixture part that covers an outlet box, attachment point or the decorative piece used to cover the electrical wires and mounting hardware.

Compact Fluorescent Lamp (CFL) - Fluorescent lamps that are single-ended and that have smaller diameter tubes bent to form a compact shape, some with integral ballasts and medium or candelabra screw bases for easy replacement of incandescent lamps.

Center Beam Candlepower (CBCP) - The luminous intensity at the center of the beam, measured in candelas, of a blown or pressed reflector lamp (such as a PAR lamp).

Centigrade (C) - Celsius temperature scale where 0°C = 32°F.

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.

Circuit Breaker - Protecting device in the electrical panel that disrupts the electrical path if overloaded.

Circuit - Wiring path for electricity.

Color Rendering Index (CRI) - An international system used to rate a lamp's ability to render objects' colors (color rendition). The higher the CRI (based upon a 0-100 scale) the richer colors appear. CRI ratings may be compared, but a numerical comparison is only valid if the lamps are close in color temperature.

Color Temperature (Correlated Color Temperature - CCT) - A number indicating the degree of "yellowness" or "blueness" of a white light source. Measured in Kelvin, 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 absolute temperature of a blackbody whose chromaticity most nearly resembles that of the light source.

Compact Fluorescent Lamp (CFL) - Light bulbs that use up to 75% less energy than most incandescent lamps, produce 75% less heat, and last up to 10,000 hours or about 7 years.

Contrast - The ratio of the luminance of an object to that of its immediate background. The angle of incidence is the angle between the normal to the surface and the direction of the incident light.

Controller - A device that controls the output of color-changing and tunable white lighting fixtures with software for lighting design and hardware components for sending control data to fixtures.

Cool White (CW) - A lamp's color temperature of approximately 4100 K.

Cove Lighting - Lighting comprising sources shielded by a ledge or molding, while distributing light above the upper wall and on the ceiling.

cUL - Underwriter Laboratories in Canada.

Current Type (AC/DC) - Operational voltage based on either Alternating Current or Direct Current.

Cutoff angle - The critical viewing angle beyond which a source can no longer be seen because of an obstruction (such as a baffle or overhang). The angle, measured up from nadir, between the vertical axis and the first line of sight at which the bare source is not available.


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Daylight Harvesting - Lighting design for building interiors that uses daylight to reduce energy consumption.

Dichroic Reflector - A reflector (or filter) that reflects one region of the spectrum while allowing the other regions to pass through.

Die-cast – A term that refers to the process of forcing molten metal, under great pressure, into a die or form to give it a specific shape. A very efficient process, excess material can be reused for future casting.

Diffusers - Those surfaces and glazing materials that redistribute some of the incident flux by scattering light in different directions.

Dimmable - The variation of lumen output while maintaining reliable performance.

Dimmer, Dimming Control - A device used to control the intensity of light emitted by a luminaire by controlling the voltage or current available to it, reducing the wattage, saving energy and changing the effects.

Diodes – Semiconductors similar to a computer chip that emit light when electricity is applied to them.

Direct Lighting - Lighting that involves luminaires that distribute 90 to 100 % of the emitted light in the general direction of the surface or object to be illuminated, usually in a downward direction.

Downlight - Small direct lighting unit that directs light downward and can be recessed, surface mounted, or suspended. Eg. WAC offers award-winning LEDme™ LED Recessed Downlights.

Duorail™ - The smallest 2-circuit low voltage rail system available, the WAC Duorail™ features one slender profile with the power of two circuits. At just ¾ inches tall and a half-inch wide, Duorail™ offers a decorative lighting solution that employs a broad range of Quick Connect™ pendants and fixtures.


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Efficacy - The effectiveness of a light source to convert electrical energy to lumens of visible light. A measure of the luminous efficiency of a radiant flux, expressed in lumens per watt as the quotient of the total luminous flux by the total radiant flux. For electric sources, this is the quotient of the total luminous flux emitted by the total lamp power input.

Efficiency - The efficiency of a light source is simply the fraction of electrical energy converted to light or the percentage of the lamp lumens that actually comes out of the fixture

Electrical Testing Laboratory (ETL) - Independent testing laboratory that performs ballast tests and certifies accuracy of performance data.

Electromagnetic Ballast (Magnetic Ballast) - A ballast used with discharge lamps that consists primarily of transformer-like copper windings on a steel or iron core.

Electronic Ballast - A fluorescent high frequency electronic ballast that uses solid-state electronic components and typically operates fluorescent lamps at frequencies in the range of 25-35 kHz. The benefits include increased lamp efficacy, reduced ballast losses, and a lighter, smaller design compared to an electromagnetic ballast. It may be used with HID (high intensity discharge) lamps.

Elliptical Reflector (ER) Lamp - An incandescent lamp with a built-in elliptically shaped reflecting surface that produces a focal point directly in front of the lamp while reducing the light absorption in some luminaires and is effective at increasing the efficacy of baffled downlights.

ELV-type Dimmer - An electronic low voltage dimmer used to dim LED lighting fixtures with electronic transformers.

Energy Star - A United States government program created in 1992 by the US Environmental Protection Agency in an attempt to reduce energy consumption and greenhouse gases. What began as a voluntary labeling program has grown into one of the largest efforts worldwide to promote energy efficient consumer products.

Energy Policy Act (EPACT) - Comprehensive 1992 energy legislation passed by the U. S. Congress that includes lamp labeling and minimum energy efficacy (lumens/watt) requirements for many incandescent and fluorescent lamps.


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Flexrail1™ - WAC's flexible, single-circuit line voltage rail system that uses hundreds of low and line voltage Quick Connect™ pendants and fixtures.

Flexrail2™ - WAC's two-circuit, line voltage bendable rail system that uses low and line voltage spots, floods, pendants, CFL wall washers and HID accent lights.

Flux - The measurement of the light intensity produced by a lighting fixture. The rate of the flow of light per unit of time expressed in lumens per square meter.

Flood Spread - Beam pattern of a reflector lamp, which disperses the light over a wide beam angle, typically 20-60 degrees, with Narrow Flood to Wide Flood designations.

Fluorescent Lamp - A high efficiency lamp utilizing an electric discharge through inert gas and low-pressure mercury vapor to produce ultraviolet (UV) energy generated by the discharge into light.

Foot Candle - A standard measurement of illuminance or light falling on a surface, representing the amount of illuminance on a surface one-foot square on which there is a uniformly distributed flux of one lumen. One footcandle is equal to one lumen per square foot and one foot in distance from the light source.

Four-Pin Compact Fluorescent Lamp - A "plug-in" compact fluorescent lamp with 4 pins in the base to make electrical contact with the ballast.


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General Lighting - Lighting designed to provide a substantially uniformed illuminance throughout an area.

Glare - Visual discomfort or loss in visual performance and visibility caused by excessive brightness.


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Halogen Lamp - A halogen lamp is an incandescent lamp with a filament that is surrounded by halogen gases that allow the filaments to operate at higher temperatures and higher efficacies, and prolonging lamp life. Produces crisp white light.

Heat Sink - A section of the thermal system that conducts or convects heat away from LEDs, extending lamp life.

HID – Stands for High Intensity Discharge, also referred to as Metal Halide lamping.

High Efficiency (Energy Saving) - Electromagnetic Ballast Ballast with core and coils, designed to minimize ballast losses compared to the "standard" ballast.

High Power Factor - A ballast with a power factor corrected to 90% or greater by the use of a capacitor.

High-Pressure Sodium (HPS) - Lamp HPS lamps are high intensity discharge light sources that produce light by an electrical discharge though sodium vapor operating at relatively high pressures and temperatures.

Hybrid LED/OLED Luminaire - WAC's innovative luminaire that merges LED and OLED technology to be used in their most salient functions, and represents the first of its kind.


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IALD - International Association of Lighting Designers

IES - Illuminating Engineering Society

Illuminance - The density of incident luminous flux on a surface or plane; illuminance is the standard metric for lighting levels, and is measured in lux (lx) or footcandles (fc). It is also called light level (lumens/m2 =lux), the intensity or degree to which something is illuminated (it is not the amount of light produced by the light source).

Illumination - An alternative term for illuminance and frequently used to designate the act of illuminating or lighting a space.

Incandescent Lamp - Typical incandescent refers to A, G, candelabra and halogen light bulbs that generate light utilizing a thin filament wire heated to white heat by an electric current passing through it.

Indirect Lighting - The lighting of a space (such as a cove) by directing the light from luminaires upwards towards the ceiling or wall using an inconspicuous light source.

Input Voltage - Power supply voltage required for proper operation of fluorescent, transformers, HID ballast or LED drivers.

InvisiLED® - WAC's LED tape light system that is easy to install, highly customizable and virtually invisible with constant color or color changing options, for indoor or outdoor applications.


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Kelvin - A unit of measurement for color temperature of a light source, ranging from warm white in the 2700K-3000K range; cool white (4100K) and natural daylight (6000K).

Kilowatt (kW) - The measure of electrical power equal to 1000 watts.

Kilowatt Hour (kWh) - The standard measure of electrical energy and the typical billing unit used by electrical utilities for electricity use. A 100-watt lamp operated for 10 hours consumes 1000 watt-hours (100 x 10) or one kilowatt-hour. If the utility charges $.10/kWh, then the electricity cost for the 10 hours of operation would be 10 cents (1 x $.10)


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Lamp - An electrically energized source of light, commonly called a bulb or tube. The complete light source package, including the inner parts as well as the outer bulb or tube. Also refers to a portable luminaire.

Lamp Life (or 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 has depreciated.

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)

Lamp Watts - Input power used to operate lamps.

LED -  A Light Emitting Diode or an electronic semi-conductor device that emits light when an electric current passes through it. Considerably more efficient than an incandescent bulb, and rarely burns out.

LED Chip - The light-producing semiconductor that may be incorporated into an LED.

LED Driver - An electronic circuit that converts input power into a current source and protects LEDs from normal voltage fluctuations, overvoltages, and voltage spikes.

LED Luminaire - A type of solid-state lighting (SSL) that uses light-emitting diodes (LEDs) as the source, optics to distribute the light, an electronic driver to control the electrical current, and thermal management to protect the LEDs.

LED Light Engine - An integrated assembly comprised of LEDs or LED arrays, LED driver, and other optical, thermal, mechanical, and electrical components.

LEDme® - WAC Lighting's complete line of energy efficient LED pendants, downlights, fixtures and luminaires for a broad range of applications.

LED Module - A single LED device or group of self-contained LED devices designed either to function on their own or to plug into a compatible LED fixture.

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

Light - Radiant energy that is capable of exciting the retina and producing a visual sensation, sometimes designated as light.

Light Bar - WAC luminaire used primarily for under cabinet and display lighting offered with LED, halogen and fluorescent lamping.

Linear Track- WAC's innovative, miniature track system for accent, cove and under cabinet applications that can be used with Quick Connect™ pendants and fixtures.

Louver - Series of baffles used to shield a source from view at certain angles, to absorb, block, reflect or redirect light.

Lumen - A lumen is a unit of standard measurement used to describe how much light is contained in a certain area. The lumen is part of a group of standard measurements known as the photometry group, which measures different aspects of light. This group also includes such units as the candela, which measures luminance, and the lux, which measures illuminance.

Lumen Depreciation - The decrease of lumen output over time, caused by bulb wall blackening, phosphor exhaustion, filament depreciation and other factors.

Luminaire - A complete lighting unit consisting of a lamp (or lamps), ballast (or ballasts) as required together with the parts designed to distribute the light, position and protect the lamps and connect them to the power supply. A luminaire is often referred to as a lighting fixture.

Luminance - A measure of "surface brightness" when an observer is looking in the direction of the surface. It is measured in candelas per square meter (or per square foot) and was formerly referred to as "photometric brightness.

Lux (lx) - The unit of illuminance equal to one lumen per square meter.


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Medium Base - Usually refers to the screw base typically used in household incandescent lamps.

Mercury Lamp - A high-intensity discharge light source operating at a relatively high pressure and temperature in which most of the light is produced by radiation from excited mercury vapor.

Metal Halide Lamp - A high intensity discharge light source in which the light is produced by the radiation from mercury, plus halides of metals.

Mounting Height - Distance from the ceiling plane to the top of the pendant or suspended track or rail system, depending on usage.

MR-16 and MR-11 - Low voltage compact reflector halogen lamps used for accent and spot lighting.


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Nanotechnology - The study and development of manipulating matter, devices and other structures on an atomic and molecular scale, to allow functional items to be extremely small, from 1 to 100 nanometers in size (one billionth of a meter).

National Electric Code (NEC) - A nationally accepted electrical installation code to reduce the risk of fire, developed by the National Fire Protection Association.


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Organic Light-emitting Diodes (OLED) - Organic light-emitting diodes (OLEDs) are based on organic (carbon based) materials. In contrast to LEDs, which are small point sources, OLEDs are thin films of small organic molecules in a crystalline phase, or a flexible polymer, that create light with the application of electricity. OLEDs are still being developed as a practical illumination source.


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PAR Lamp - Parabolic aluminized reflector lamp utilizing an incandescent filament, a halogen filament tube or a HID arc tube. PAR lamps rely on both the internal reflector and prisms in the lens for control of the light beam.

Pendant - A luminaire that is suspended from a ceiling, a canopy, a track or rail.

Photometry (Photometrics) - The measurement of a fixture's or lamp's optics including luminance, luminous flux, luminous intensity, and spectral distribution of visible light.


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Quick Connect™ Pendants and Fixtures - Luminaires designed with an innovatively engineered adapter to be operated on a broad range of track, monorail and canopy systems.


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Reflectance - The ratio of light reflected by a surface to the total amount of radiation incident on the surface.

Reflector Lamp (R) - A light source with a built-in reflecting surface including R, PAR and MR lamps.

Reflector - Device used to redirect the flux from a source by the process of reflection.

Responsible Lighting - WAC's brand standard that reflects the company's holistic approach to business, encompassing a deep commitment to responsible eco-friendly manufacturing, extensive research/development, energy saving technology, and altruism.


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Shade - Screen made of opaque or diffusing material designed to prevent a light source being directly visible at normal angles of view.

Self-Ballasted Lamps - A discharge lamp with an integral ballasting device allowing the lamp to be directly connected to a socket providing line voltage.

Semiconductor - A material that has an electrical conductivity between that of a conductor and an insulator. Devices made from semi-conductor materials are the foundation of modern electronics.

Solid State Lighting - A type of lighting that uses semiconductor light-emitting diodes (LEDs), organic light-emitting diodes (OLED), or polymer light-emitting diodes (PLED) as sources of illumination rather than electrical filaments, plasma (used in arc lamps such as fluorescent lamps), or gas. The term "solid state" refers commonly to light emitted by solid-state electroluminescence, which creates visible light with reduced heat generation or energy dissipation.

Specular Reflection - Reflection from a smooth, shiny surface, such as specular aluminum or often called to as Alzak.

Spot - A luminaire or 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.

Surface Mounted Luminaire - A fixture that is mounted directly on a ceiling.

System - The lamp and ballast combination, and sometimes the entire lighting delivery system including the fixture, optics, and layout. Eg. WAC offers a variety of systems including Solorail™, Duorail™, Flexrail1™, Flexrail2™ and InvisiLED®.


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T-8, T-5 - A designation for the diameter of a tubular bulb, usually fluorescents, in eighths of an inch; T-8 is one inch, T-5 is five eights of an inch.

Task Lighting - Supplemental lighting provided to assist in performing a localized task, e.g. a light bar to under counter, or track fixtures to illuminate art on a wall.


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UL Listing – UL stands for Underwriters Laboratory. It is a trusted resource across the globe for product safety certification and compliance solutions.

Underwriters' Laboratories (UL) - A private organization which tests and lists electrical and lighting equipment for electrical and fire safety according to recognized industry standards.


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Valence Lighting - Upward or downward cove lighting from light sources on a across the top of a window or along a wall typically above eye level and shielded by horizontal panels; generally light that is projected towards ceiling.

Volt - A measurement of the electromotive force in an electrical circuit or device expressed in volts.

Voltage - 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-volt) refers to the line voltage that it must be connected to.


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Warm White Light (2700K-3000K) - A yellowish light that helps enrich the warm colors in your home and are suitable for lounges, hallways, bedrooms and other areas where people relax.

Watt - The unit of electrical power used to indicate power consumption, as used by an electrical device during its operation.


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Zigbee - is targeted at radio-frequency (RF) applications that require a low data rate, long battery life, and secure networking.


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