Acronym for alternating current, which explains a source where the voltage adjusts polarity numerous times per second, with a frequency of 50 Hz or 60 Hz depending on the nation.

Accent Lighting

Lighting that concentrates its output in a narrow beam of light, accentuating specific decorative features or items, making them stick out from their surroundings. Accent lighting is also valuable in retail applications, where it can be used to draw attention to particular items and also make them seem extra enticing.


American Lighting Association, a trade organization that encompasses the U.S.A., Canada and also the Caribbean, focusing on household lighting. ALA participants consist of manufacturers, event coordinators as well as developers.

Ambient Lighting

General lighting used to give presence in a developed atmosphere. Ambient lighting consists of both synthetic as well as all-natural lighting, and does not include task lighting or accent lighting.


Measurement system for electric current. In lighting installations, wiring and also protections are determined based upon the amperes drawn by the lights circuits, along with their rated voltage.


See Ampere.

Amp Calculations

Procedure for figuring out the current attracted by a lighting fixture or a circuit consisting of several fixtures. Once the current drawn in amperes is known, it is feasible to size the cable for the lighting circuit, in addition to the electric protection devices.

Angle of Light

Angle between the alignment of a source of light and the viewing direction. For example, the angle of light is zero degrees when taking a look at a downlight straight from below, and increases gradually as the viewer steps away from it.

The term is commonly used in theatrical lighting, to explain the angle in between the stage lighting direction as well as the viewer’s line of vision.


American National Standards Institute, a publisher of standards for United States product or services. ANSI likewise collaborates nationwide and international requirements, allowing United States products and services to be utilized somewhere else.

ANSI Ballast

A ballast that abides by ANSI criteria. See Ballast


The planned use of a lighting product. Residential, retail, hospitality, medical care as well as high-bay industrial are all instances of lighting applications.

Arc Lamp

Any type of lamp that develops an electric arc in between 2 electrodes. Arc lamps normally boost a gas, making it glow as well as generating an illumination output.

Architectural Lighting

Design lighting that is part of a structure’s style as well as construction. It likewise gives ambient lighting as a secondary feature.


A chemical element, and also one of the noble gases. It is utilized inside the bulbs of incandescent lights to prevent oxidation of their filaments. Argon can also be utilized in gas-discharge lights to produce violet light, or blue if mixed with mercury.



The lighting output of exterior fixtures that is sent out opposite to the designated direction, normally an unwanted result. For instance, if the pole lights in a parking lot give off backlight towards adjacent houses or condos, it can be aggravating for the property owners.

Backlight should not to be confused with backlighting, an accent lighting method.


Lighting designed to light up an item from behind, which triggers an enticing radiance impact around its sides. Backlighting is a type of accent lighting, and is commonly used to draw attention to works of art.

Backlighting must not to be confused with backlight, an undesirable lighting result that can be generated by outdoor fixtures.


An opaque or transparent element that obstructs direct view of an illumination source.


A component required by fluorescent as well as HID illumination fixtures. It controls the voltage and electric current supplied to the light during ignition and also operation, protecting against overheating or early failure. Depending upon their inner construction, ballasts can be either magnetic or electronic.

Ballast Factor (BF)

A ballast factor is a number, commonly in between 0.70 and 1.2, that tells you just how much light a lamp will give off with that ballast. Ballast factor is determined by separating the lumen output of a lamp-ballast combination by the lumen output of the exact same lamp(s) on a reference ballast.


The part of a lamp that attaches to the illumination fixture, supplying both physical assistance and also electrical power for the light. A light and also component can just be used together if the lamp base matches the fixture outlet. The bases of a lot of residential lights utilize either a screw or numerous pins.

A light can have more than one base: for instance, fluorescent tubes have one on each end.

Base Temperature

Maximum permitted temperature of a light base, which needs to be thought about when designing the lighting component.


A light base that connects with the socket making use of keyways as opposed to threads.

Beam Angle

Also referred to as beam spread, the light beam angle is a value that defines the descending light cone emitted by an illumination component with a reflector. The beam angle is measured between the downward direction, where the lamp gives optimum illumination intensity, and also the direction in which intensity drops to 50%. In other words, a light with a huge beam angle spreads its illumination into a wider cone.

Bi-Pin Base

A light base that makes use of 2 pins, as implied by its name.


A kind of illumination fixture generally utilized outdoors, consisting of a short and also wide post with a light on top. Bollards typically achieve a dual function, offering both outdoor lighting as well as design.

BUG Rating

BUG is an acronym for backlight, uplight as well as glare, and the term was developed by the Illuminating Engineering Society (IES) and International Dark-Sky Association (IDA) to explain the quantity of light given off by a fixture in unwanted directions.

Backlight is routed behind the luminaire.

Uplight is directed upwards.

Glare triggers a visual impairment (See Glare).

In the BUG rating, these impacts are suggested in a scale from 0 to 5, where 0 shows the effect is lessened and 5 suggests it is not controlled whatsoever. For that reason, the very best feasible BUG score is B0 U0 G0, and thus the worst score is B5 U5 G5.


A clear casing which contains a light source, typically made from glass.

Burn Position

The operating setting for which a light is designed. For example, some lights can only operate in the base-up placement. Lights operating in positions for which they are not designed typically suffer decreased efficiency or short-term failing.



Common term for the casing of a recessed downlight.

Candela (cd)

Measurement unit for luminescent intensity which is the quantity of light discharged in a specific direction. Not to be confused with the lumen (lm), dimension unit for the overall illumination output of a light or fixture, without defining a certain direction.

Cave Effect

An effect that occurs when lighting fixtures direct their illumination downward and therefore little or no light is reflected back up in the direction of the ceiling or upper wall sections. The cavern effect is generally undesirable since it makes indoor spaces feel dark, like the interior of a cavern.


Part of a light’s component that covers the outlet box as well as wiring connections. Canopies typically have decorative features.


Certifies Ballast Manufacturers Association, a company that certifies ballasts as required by ANSI criteria. Ballasts with the CBM seal have a guaranteed minimum ballast variable of 0.85 (See Ballast Factor).

Ceiling Cavity

The part of a room that is above the illumination components.


International Lighting Commission (French: Commission internationale de l’éclairage), a reliable organization in the lighting sector around the world.


Derived from “chandler” (candle light maker), a chandelier is a decorative light that hangs from the ceiling and consists of numerous branch-like parts that hold lights or candles.

Circline Lamp

A subtype of fluorescent light where a fluorescent tube is bent into a circular shape, and also where the ballast is normally situated between.

Circuit Breaker

Electric protection device that is generally situated within a distribution board. Each illumination circuit is attached to a circuit breaker, and it interrupts current instantly if an overload or fault is found.

Coefficient of Utilization (CU)

The fraction of a light’s luminescent output that reaches the work plane. The CU is affected by the luminescent performance of the fixture, in addition to room geometry as well as colors.

Cold Cathode Fluorescent Lamp (CCFL)

A fluorescent lamp that sends out electrons without warming its electrodes, using only a high voltage (conventional fluorescent lamps utilize voltage and heating). CCFLs tend to be much less efficient than conventional fluorescent lamps, however provide a life span of over 60,000 hrs, similar to that of LED lighting.

Color Rendering Index (CRI)

A metric utilized to define just how consistently a source of light can render the true shades of objects and spaces, where natural source of lights like the sun have a perfect index of 100. Using lamps with a high CRI level is really vital in high-end interior design, as they enhance the exposure of decor as well as the fine details.

Continuous Dimming

Dimming technique where the light output can be adjusted at any type of degree in between OFF and 100% output, without incremental steps. See Dimmer.

Compact Fluorescent Lamp (CFL)

A kind of fluorescent light where the tube is curved into a small shape to decrease area requirements, hence its name. CFLs frequently have an integrated ballast as well as screw bases, enabling them to change incandescent and also halogen bulbs directly

Cool White

A light with an associated color temperature level of around 4100K. The term comes from the fact that light sources at this color temperature level value do not have the particular yellow shade of incandescent bulbs or warm white LED lights.

Cornice Lighting

Fluorescent light built right into a soffit at the top edge of a wall surface (i.e., where the wall surface meets the ceiling).

Correlated Color Temperature (CCT)

Unlike the CRI, which explains how consistently a light represents other objects, the associated shade temperature level (CCT) explains the color result of the light itself. Some typical CCT values include

2700K, with a warm shade of yellow that produces enticing and also soothing environments

4000K, a neutral white tone that is a perfect balance between relaxation and concentration

6500K, with a slight shade of blue, which has a stimulating effect

Although the correct technical term is correlated color temperature level, it is typically shortened to only color temperature level. It is likewise important to keep in mind that the CCT is not the actual operating temperature level of a light – it is the temperature to which you would need to heat a blackbody to make it glow with the exact same color. For example, an LED light bulb with a CCT of 5000K glows in the exact same color as a blackbody warmed to an actual temperature of 5000K, yet the LED light bulb itself does not get to that temperature.

Cove Lighting

A type of illumination that typically guides its outcome in the direction of the ceiling, and where individual fixtures are concealed in ledges. Cove lighting is typically utilized for ornamental functions due to the fact that it can emphasize the boundaries of wall surfaces, along with ceiling features.

Crest Factor

In a ballast, the ratio of optimal light current to average operating current. The service life of lights tends to be extended as the crest variable comes to be reduced.

Cutoff Angle

Stops light from being emitted over the horizontal plane. With complete cutoff, no light is given off at or above an angle of 90 degrees from the nadir (horizontal plan).



Acronym for Digitally Addressable Lighting Interface, a communication method for lighting automation.

Daylight Harvesting

An illumination design method that takes full advantage of making use of natural light to reduce energy costs as well as create indoor areas that really feel natural as well as appealing.

Daylight Lamp

A light with a CCT value similar to that of daylight, typically in between 5500K and 6500K. It is important to keep in mind that the term does not describe real daytime, however rather artificial illumination that reproduces its color.


Phrase for Direct Current. Used to define a power supply where the flow of electricity always occurs in one direction, such as that supplied to LED arrangement by their drivers.

Desk Lamp

A small fixture used for task lights on a desk, and is normally portable.

Diffused Light

Light created by a prolonged surface area, either straight or through reflection. Diffused light provides an uniform and soft distribution that lessens shadows.


A piece of glass or acrylic that has the function of spreading the light from a light bulb, which results makes lighting more uniform as well as removes glow.


Adjective to describe a lamp or component whose lighting output can be regulated with a dimmer. See Dimmer.


A device that controls the lighting output of a lamp by regulating the power provided. Dimmers can be utilized to make indoor settings more personalized and also customizable, and are likewise useful to save energy. It is important to note that not all lights are compatible with dimmers, and incompatible types might be harmed.

Direct Lighting

Illumination where most of the light goes straight from the source to the area you wish to brighten.

Directed Light

Light produced by point surfaces, which causes a focused result that emphasizes edges as well as shadows. Directed light usually causes glare when the sources is viewed straight.


A compact illumination fixture that routes its output downward, hence its name. Downlights can be recessed, pendant or surface-mounted.


A piece of electronic equipment that changes the major supply voltage into a reduced DC voltage that is appropriate for LED illumination. Some LED lamps have an integrated driver, while others require one to be connected externally, much like the ballasts utilized by fluorescent and HID lights.


Edge Lit LED

A type of LED fixture that uses a clear acrylic pattern with etched dots, lines or patterns. The panel is surrounded by a variety of LEDs, and the etched pattern refracts the light consistently in all directions.


Describes how efficiently a lighting fixture can transform electrical power into lighting, measured in lumens per watt. This is like the gas mileage of a car, where the lights output can be compared to miles traveled, and also the electrical power input is like fuel consumption.


Conversion proportion between illumination power output as well as electrical power input, gauging both amounts in watts. Not to be confused with efficacy, which defines the proportion in between lumen output and also watts consumed.

Since lumens describe lighting outcome far better than watts, effectiveness often tends to be a lot more useful concept in illumination design.

Electromagnetic Ballast

See Magnetic Ballast.

Electronic Ballast

A subtype of ballast that uses power electronics to offer a high-frequency voltage and regulated current for fluorescent lights. Digital ballasts are lighter and also much more efficient than magnetic ballasts, and they remove humming and also flickering concerns.

Electronic Transformer

Smaller as well as lighter than magnetic transformers, electronic variations utilize electronic switching as well as special dimmers to step the line voltage down to the light voltage.

Ellipsoidal Reflector Lamp (ER Lamp)

This soft glass light gathers and mirrors light via a barrel about 2″ in front of the fixture.

Emergency Lighting

Lights designed to provide exposure when the regular illumination system falls short, for instance during power outages. Emergency lights are geared up with batteries, enabling it to operate in enough time for a building to be evacuated.

Energy Star

A energy saving sustainability program created by the United States Division of Energy as well as the Environmental Protection Agency. Lighting products with the ENERGY STAR have been tested for premium energy efficiency.


Energy Policy Act, a 1992 regulation that developed minimum efficacy demands for incandescent and also fluorescent lights, a well as labeling requirements.



The wire coil that is heated up to generate lights in incandescent as well as halogen lamps, usually made from tungsten.

Flat Panel Top LED

A low-profile LED fixture that utilizes an edge-lit panel, created to change linear as well as parabolic fluorescent fixtures. This component type is readily available in recessed, surface-mounted and pendant versions.


A phenomenon where a light blinks repetitively, often brought on by power supply problems, or a damaged ballast or driver.


High-power illumination fixtures that usually use HID light bulbs or their LED equivalents. They are generally utilized outdoors to highlight specific objects or areas.

Fluorescent Lamp

Among the primary kind of lighting, much more effective than incandescent and also halogen bulbs, however topped by LED lights. A fluorescent light makes use of electrodes to boost mercury vapor and produce ultraviolet (UV) radiation, which in turn boosts the phosphor layer of the light to produce noticeable light.

Fluorescent Tube

A certain type of fluorescent lamp that has a tubular form and also comes outfitted with pins at its ends, to be attached to the voltage output of a magnetic or digital ballast. Fluorescent tubes are assigned by the letter “T” followed by a number indicating its size in 1/8ths of an inch:

  • T12 = 12/8” or 1.5”
  • T8 = 8/8” or 1.0”
  • T5 = 5/8″ or 0.625”
  • Fluorescent tubes can be found in standard sizes, where a few of the most common are 24″ (2′), 48″ (4′) and also 96″ (8′).

Flush Mount Lighting / Flush Mount LED Lights

This type of light is placed on the ceiling with little or no gap in between the ceiling and the light.

Focused Light

See Direct Light.

Foot-candle (fc)

Measurement system for illuminance, or lumens per unit of area. One foot-candle is equivalent to one lumen per square foot (See Illuminance).

Frosted Lens

A white lens that is translucent yet not clear, which diffuses the output of a light.



Visual impairment triggered by a brilliant source of light, directly noticeable or reflected by a surface. There are two kinds of glare:

Discomfort glare creates an instinctive response to close the eyes as well as avert. This is the type of glare felt when subjected to a powerful HID light or when the sunlight is directly noticeable through a window.

Disability glare hinders vision, but does not cause the same reaction as discomfort glare. If a light source is reflected on your phone screen, as an example, it does not bother your eyes yet distinguishing items on the screen may be difficult.


Hard Light

A light that produces darkness with an extremely sharp edge when cast on items. Direct lighting from a concentrated source is usually hard light.

See Soft Light.

Halogen Lamp

An enhanced variation of incandescent lights, where the glowing filament is included in halogen gas, thus its name. Halogen lights are around 25% much more reliable than their incandescent counterparts.

Heat sink

A lamp or luminaire element that is used to dissipate heat successfully. Warm sinks normally use products with a high thermal conductivity as well as have a fin-like geometry to make sure that their surface area in contact with the air is optimized.


Acronym for high-intensity output, a kind of lighting commonly used for commercial and outdoor settings as a result of its powerful output. Some examples of HID illumination are mercury-vapor, metal-halide, xenon, high-pressure sodium and low-pressure sodium lamps.

All kinds of HID lights produce lights by stimulating an enclosed gas with an electrical arc, and as a result they run at high temperatures.

High-Bay Lighting

Illumination systems made for ceiling elevations of 25′ or higher, typically found in sporting facilities, warehouses or industrial locations.

See low-bay lighting.

High-Efficiency Plasma (HEP)

An arising illumination innovation that uses radio frequency to boost a contained gas and also create a tiny yet very bright round of plasma. HEP illumination provides extremely high efficiency (over 90 lumens per watt) as well as ideal color rendition (CRI = 100).

The technology ended up being commercial very recently, nevertheless, and has actually not accomplished a market share similar to that of LED.

High-Output (HO) Lamp

Fluorescent tubes with a greater lumen output and rated power than traditional fluorescent tubes.

High Voltage Lamps

Lamps that work at a high voltage and offer naturally diffused or scattered light.


Phrase for high-pressure sodium, a subtype of HID lighting where excited salt vapor is the source of light. The illumination result of HPS lamps is characterized by its warm yellow shade, and also they are generally utilized in cobra-head street lights



International Association of Lighting Designers, a global association that promotes ideal practices in lighting layout, while offering training and scholarships.


Institute of Electrical and Electronic Engineers, a worldwide professional association with over 400,000 members. The IEEE is a technological authority that has published many requirements and recommended practices for the electric and digital areas.


Illuminating Engineering Society of North America, a technical authority in the lights sector, with lots of publications to its credit. IESNA has participants and also recognition throughout the globe.


The luminous flux on a surface, per unit of location. The illuminance requirement of developed settings are determined by their designated purpose, and there are two typical unite of dimension:

Lux – Equal to one lumen per square meter.

Foot-candle – Equal to one lumen per square foot.

Greater illuminance levels make surfaces appear brighter to the human eye and also improve visibility


The action of providing or brightening up with light or the resulting state. The use of lighting for practical or artistic purposes.


Emitting light as a result of being heated up.

Incandescent Lamp

A kind of lamp with a tungsten filament that glows when it carries current. Incandescent illumination has a perfect color-rendering index of 100, similar to that of the sun, yet is amongst the least efficient kind of lighting.

Indirect Lighting

Lighting strategy based on reflecting the output of a light on surfaces. An example is the illumination given by torchiere fixtures, which produce their light beam towards the ceiling to be reflected down.

Induction Lamp

A kind of gas-discharge lighting where the gas is not stimulated directly by electrodes, like in fluorescent or HID lights, and where microwaves or radiofrequency are utilized instead. Induction illumination has a much longer life span than HID or fluorescent lighting due to the fact that there are no electrodes being subject to use each time the light is triggered.

Initial Lumens

Illumination output of a brand-new lamp, which decreases with use.

See Mean Lumens.

Instant Start Ballast

A kind of fluorescent illumination ballast that applies a high-voltage pulse to the lamp, making it begin immediately without pre-heating the electrodes. The drawback of instant-start ballasts is that they reduce the service life of lights: electrode material is expelled each time the light is started, blackening its edges as well as causing eventual failure.

Insulated Ceiling (IC) Fixture

These lighting fixtures are set up into the ceiling and remain in direct contact with insulation. They have a lower wattage as well as send out less heat.

Integrated Lighting Fixture

A type of lighting component that supplies exceptional energy performance, by utilizing a specially-designed LED range as well as internal geometry. Integrated illumination components are typically much more effective than lamp-based LED fixtures, but they make retrofits more expensive since the entire fixture has to be replaced, not just the lights as well as the ballasts.

Interior Soffit Lighting / Soffit Light Fixtures

Lights for parts of the ceiling that are lower than the primary surface area; for example, the fixtures set up above the kitchen sink or on a beam or the bottom of a porch.

International Dark-Sky Association (IDA)

A global authority on light pollution as well as ecologically accountable exterior lighting. Their major objective is to protect evening skies visibility throughout the globe.

Ingress Protection (IP) Rating

Ingress Protection ranking, a two-digit code that suggests the resistance of a lighting component to solid particles and liquids, where higher numbers indicate improved protection. The very first number suggests defense against solids, and the second indicates the defense level against liquids.

For example, an IP60 has a higher degree of protection than an IP50 rating.


Kelvin (K)

Measurement system for temperature, although in the illumination industry it is more frequently utilized to indicate the correlated color temperature (CCT) of lights.

Kilowatt (kW)

Measurement unit for electric power, equal to 1000 watts. This term needs to not be interchanged with kilowatt-hour.

See Watt.

Kilowatt-hour (kWh)

Measurement unit for energy usage. As indicated by its name, it is equivalent to the quantity of energy consumed by a one-kilowatt appliance running for 60 minutes. Electric energy costs are commonly computed based on kilowatt-hour consumption each month. This term should not be confused with kilowatt.



The process of fusing together thin sheets of material to ensure that the composite material is stronger and more secure.


The detailed part of a light fixture that emits light. They generally feature conventional bases that fit into the sockets located in compatible fixtures. Some lamps have built-in ballasts or drivers, while others are attached to an exterior one included in the fixture.

Lamp Lumen Depreciation (LLD)

A progressive reduction in the luminescent output of a lamp throughout its life span.


The part of a light fixture that offers support as well as power for a light with a matching base.

Layering Light

An interior design approach where several kinds of lighting are integrated to achieve a particular atmosphere or mood.


Acronym for light-emitting diode, a solid-state component that emits light when exposed to electrical current. LED illumination represents the cutting edge in the industry, outclassing most other sorts of lights in terms of energy effectiveness, layout flexibility and also colors of light readily available.

LED Array

A group of LEDs installed on a printed circuit board, with the ability of creating a lighting output.


Leadership in Energy and Environmental Layout, a resource efficiency accreditation framework for structures, created by the United States Green Building Council.


Lamp or luminaire element that has the objective of spreading the illumination output to make sure that the preferred distribution pattern is attained.

Lensed Troffer

A troffer-type luminaire that is covered by a lens, making the lighting distribution more uniform as well as getting rid of glare.

Light Loss Factor (LLF)

A factor utilized in illumination design to represent the deterioration in luminous outcome gradually over time. The LLF make up several facets such as reflector or lens deterioration, dust buildup, light degradation because of voltage surges or heat, etc.

Light Pollution

Any light output sent out in undesirable directions, which might have adverse effects. An example of light pollution is when parking lot components discharge brilliant light sideways, subjecting drivers to glare.

Light Scallops

A result of a downlighting strategy. The downlights that are closest to the wall produce light scallops and add aesthetic value to a space.

Light Transformer

Additionally referred to as dimmer switches, light transformers are electrical tools that are used to alter the voltage of a circuit to make the light dimmer or brighter.

Lighting Fixture

See Luminaire.

Linear Lighting

Several LEDs (light-emitting diodes) aligned in a single strip as well as utilized for producing uninterrupted lines of directional illumination.


IESNA requirement that establishes the procedure to examine the photometric and also electrical properties of LED illumination.


IESNA requirement that establishes the procedure to evaluate the life expectancy of LED lights.


A translucent or nontransparent screen that obstructs straight visibility of a light and eliminates glare.

Low-Bay Lighting

Lighting systems made for ceiling elevations below 25′.

See high-bay lighting.

Low Voltage Fixtures / Low Voltage Lamps

Lights that run at a lower voltage than the standard household voltage. These incandescent lamps need a step-down transformer to bring the voltage down from 120 to 6, 12 or 24 volts.

Low Voltage Track

As the name suggests, this is a track that functions at a reduced voltage utilizing a step-down transformer.


Phrase for low-pressure sodium, a subtype of HID illumination where excited sodium vapor is the resource of light. LPS lights have a very high efficacy, but their shade providing performance is extremely inadequate. This limits their use to some outside applications where the CRI is not important.


Measurement unit for the lighting output of lamps or components. The total lumens produced and their spatial distribution are of critical value when developing attractive as well as elegant interior areas. In lights, lumens can be compared to miles traveled and watts can be compared to fuel consumption.

Lumen Maintenance Life

A metric utilized to define the time in which the output of a light diminishes to a certain percentage of its preliminary worth. The lumen maintenance life is measured in hours as well as shown by the letter L plus two numbers. For example, the adhering to lumen maintenance life would certainly describe a product whose result decreases to 80% after 50,000 hours of use:

L80 = 50,000 hours

Lumens per Watt

Lumens Per Watt (LPW) is the light outcome per unit of power consumption and it shows the illumination system’s effectiveness.

Lumens to Watts

The power (P) in watts (W) can be calculated by dividing the luminous flux (ΦV) in lumens (lm) by the luminous efficacy (η) in lumens per watt (lm/W).


A complex and useful light fixture. A luminaire consists of the lamp, the ballast or driver, inner circuitry, reflectors, lens as well as any type of added components required to supply light.

Luminaire Dirt Depreciation (LDD)

Progressive reduction in the output of a luminaire as a result of dust accumulation.

Luminaire Efficiency

The ratio between the lumens discharged by a total luminaire to those released by the lights within. A part of lighting is constantly shed because of interior geometric attributes and also reflections.

Do not confuse with luminous efficacy.


The brightness of an object or surface, as perceived by human sight from a particular direction. Luminance is measured in candelas per square meter (cd/m2). It is essential to note than luminance changes depending on the seeing angle, and also high luminosity values are the direct cause of glare.

Luminous Ceiling

A continuous plane of clear ceiling panels with diffusing, fluorescent strip lights.

Luminous Efficacy

See Efficacy.

Luminous Flux

Total result emitted by a light, gauged in lumens. The luminescent change defines the complete lighting output of a lights fixture without taking into consideration direction. Not to be confused with luminescent intensity.

Luminous Intensity

Illumination emission in a particular direction, measured in candelas. Luminescent strength changes depending upon the viewing angle. Not to be confused with luminous flux.


Measurement unit for illuminance, or lumens per unit of area. One lux amounts to one lumen per square meter.

A vital element of lighting design is attaining an appropriate illuminance degree depending upon the application at hand.


Magnetic Ballast

A kind of ballast that uses a ferromagnetic core, similar to that of a transformer, to regulate the power supply given to a fluorescent light. Magnetic ballast are heavier and also much less effective than their digital counterparts, and have issues with flickering or humming.

Mean Lumens

Lighting outcome of a light or luminaire at 40% of its service life.

See Initial Lumens.

Medium Base

Likewise referred to as E26 or basic base, it is the screw-shaped base utilized by many domestic light bulbs.

Mercury Lamp

A subtype of HID light that creates its lights output by promoting mercury vapor, hence its name. Mercury lamps may utilize a phosphor layer to enhance lighting efficiency, and also are frequently used in exterior as well as commercial lighting applications.

Metal Halide (MH)

A subtype of HID lamp that produces its illumination result by stimulating evaporated metal-halide compounds, thus its name. Like mercury lamps, MH lights are frequently utilized in exterior and also industrial setting.

Ceramic metal halide is a subtype of MH light, where the arc tube is made from a ceramic product instead of quartz glass. This enhances the shade rendering index of the light.

Mogul Base

Additionally known as E39 base, it is larger than the medium E26 base and also frequently utilized by HID lights. Some LED replacement lamps for HID fixtures are compatible with the same type of ballasts as well as include a magnate base to utilize the same outlet.

Monochromatic Light

A source of light whose output has one wavelength. The plain yellow lighting of low-pressure sodium lamps is an instance of monochromatic light.

Mounting Height

Mounting height can have two different definitions, depending on the application:

Range between the bottom of the fixture as well as the work plane.

Range in between bottom of the fixture and the ground.

MR Lamp

MR is an acronym for complex reflector, an element utilized to shape the result of a light bulb into a directional light beam. MR lamps normally use incandescent, halogen or HID bulbs, and there are LED substitutes readily available. MR lamps are offered with both screw bases and pin bases.

The MR classification is followed by a mathematical value suggesting the light size in 1/8ths of an inch, where two of the most usual kinds are MR11 and MR16.



National Association of Innovative Lighting Distributors, an illumination market association that offers recurring training, a discussion online forum, networking, business knowledge and information services.


National Electric Code, a publication by the National Fire Protection Association, which develops the needs for fireproof electric installments.


National Electrical Manufacturers Association, a US-based electric industry organization that establishes technical criteria to ensure item quality and also uniformity.

NEMA Enclosure Type

A numerical code that explains the degree of protection provided by an enclosure, according to the NEMA 250-214 standard. As an example:

NEMA 2 = Indoor usage, defense against falling dust as well as spilling of water.

NEMA 3R = Interior or outside usage, dust defense, resistant to rainfall as well as snow.

NEMA 4X =Indoor or exterior use, dust-tight, water-proof (including hosedown) and corrosion-proof.

NEMA 6P = All NEMA 4X benefits, and additionally submersible.


National Institute of Standards and Technology, a US-based physical scientific research lab that is a technological authority on criteria, measurements and modern technology.


Occupancy Sensor

A device that makes use of infrared or ultrasonic radiation, or audio, to identify the presence of people as well as change the lights appropriately. Occupancy sensing units are an efficient energy-saving measure.


Phrase for organic light-emitting diodes, versatile polymers based upon organic carbon molecules, where the light source is spread out across a surface area in contrast to a point source.

Opal Glass

Semi-translucent white glass that owes its milky surface to the ingredients included in clear glass. It is utilized for diffusing light.

Opaque Material

A product that entirely obstructs noticeable light.


PAR Lamp

PAR is a phrase for parabolic aluminized reflector, and it is utilized to shape the output of a light bulb into a directional light beam. PAR lamps normally make use of incandescent, halogen or HID bulbs, and also there are additionally LED replacements available. PAR lights are readily available with both screw bases and pin bases.

The PAR designation is followed by a numerical value indicating the lamp diameter in 1/8ths of an inch. Some of the most typical kinds are PAR20, PAR30 as well as PAR38.


Term used to explain a louver with a parabolic shape.

See Louver.

Pendant Light / Pendant Fixture / Pendant Lamp

An illumination fixture that is designed to hang from the ceiling, and also uses a shade to avoid glow. Pendant lights can be utilized for both general as well as task illumination.


The dimension of light as well as its properties.

Photopic Lumens

The portion of luminous output that obtains a reaction from the cones in human eyes, which are in charge of daytime vision.

Post Light

Lighting fixture utilized to give outside area lighting, where the lamp is found on top of a pole, frequently with a reflective housing that attains a particular illumination pattern.

Power Factor (PF)

Ratio of actual power to apparent power drawn by lighting fixtures as well as various other electric tools. The actual power is represented by the actual watts taken in, while the apparent power is the reproduction product of voltage and current, gauged in volt-amperes. Electric energy companies generally apply added fees if the power variable of a structure goes down below a specified degree.

Programmed Start Ballast

A ballast that pre-heats the electrodes of a fluorescent light prior to igniting it, which lowers their wear gradually and also extends the life span of the light. Preheating is completed by using an extremely reduced voltage that is high enough to raise the temperature of electrodes, yet without causing the lamp to ignite.

Pull Down Light Fixture Parts

Making use of retractable performance, this recessed downlight pulls down from the ceiling to focus on various angles.

Pulse Start Ballast

A sort of ballast used with HID illumination, which utilizes a series of controlled voltage pulses to spark the lamp, lessening damages to the electrodes each time the lamp is activated.



Energy transmission in the form of waves. Light is a form of radiation, consisting of infrared and also ultraviolet light, which are unnoticeable to human beings.

Rapid Start Ballast

A kind of ballast for fluorescent lights, which pre-heats the electrodes and uses voltage concurrently. This kind of ballast is faster than a configured start ballast, yet slower than an immediate start ballast. The resulting electrode damages when the lamp is started is intermediate between that of instantaneous start ballast (high damage) and configured start ballast (low damage), and thus the resulting life span is also intermediate.

Rated Lamp Life

The time it takes for 50 percent of the lamps in a batch to reach the end of their service life.


A cash incentive for a purchase. In the USA, lots of states have rebate programs for energy-efficient innovations (e.g. LED lights) or renewable resource systems (e.g. solar panels).

Recessed Can

A particular type of lighting fixture with a cylindrical form that is installed in the ceiling, hence its name.

Recessed Lighting / Recessed Fixture / Recessed Luminaire

Also known as pot light, canister light or downlight, recessed lighting fixtures or luminaries are mounted into the openings in a ceiling, appearing as if the light is beaming from a raised opening.


The ratio of the intensity of reflected light to that of the incident light on a surface.

Reflective Lamp Shade / Reflective Lighting Fixtures

A light or lighting fixture that creates directional beams. Reflective fixtures route all the lights descending (to ensure that there is little or no reflection of light back in the opposite direction).


An interior element of lots of lamps as well as luminaires. It has a reflective surface and also its geometry is particularly developed to offer a certain lighting distribution. Reflectors are frequently used with lights that emit light rays in every direction (HID, fluorescent, etc.) to concentrate their output in a particular direction.

Restrike Time

Time required by a HID lamp to accomplish full illumination after it has actually been switched off.


A lights system upgrade, usually with the goal of enhancing energy efficiency as well as site security.

Room Utilization Factor

The ratio of the luminous change (lumens) obtained on the work plane to that released by the light



The resulting “colorfulness” when items are exposed to a source of light, contrasted to that arising from all-natural lights. If the colors appear a lot more extreme, the light saturates them; on the other hand, if colors are dulled, the source of light desaturates them.


A wall-mounted lights component, which normally has a decorative objective.

Scotopic Lumens

The portion of luminous output that obtains an action from the rods in human eyes, which are accountable for nighttime vision.

Scotopic/Photopic (S/P) Ratio

Ratio of scotopic to photopic lumens for a specific light. As the S/P proportion rises, it implies the light is much better for simulating human eyesight, which implies the preferred illumination degree can be accomplished with a reduced power consumption.

Self-Ballasted Lamp

A lamp that has an incorporated ballast, permitting direction connection to the supply voltage. CFL light bulbs with a screw base are just one of the best-known kinds.

Semi Flush

A ceiling lighting component that has a stem that separates (or creates a visible void between) the light from the ceiling.


A display that prevents a light source from being viewed directly. Tones generally make use of opaque or clear products.

Shadow Casting Light Fixtures

Lights that are designed to cast light and darkness, creating elaborate geometrical or abstract patterns on surrounding surfaces.


See lampholder.

Soft Light

A light that develops progressive darkness, without a noticeable edge between lighted and dark locations. Soft light is typically created with scattered illumination resources, such as:

The sunlight, when covered with clouds that diffuse its light.

Illumination components with lens or diffusers.

See Hard Light.

Specular Reflection

Reflection from a surface that is smooth and also shiny, such as metal kitchenware.


Lighting component that produces a narrow descending beam, normally utilized for accent illumination or task lighting applications.


Acronym for solid state lights, any sort of lighting that makes use of LEDs to create light, instead of incandescent filaments, fired up gas or plasma. SSL includes OLEDs.

Step Dimming

Dimming technique that utilizes incremental and also set illumination levels, as opposed to gradual dimming from OFF to 100% result.

See Dimmer.

Strip Light

Versatile, dynamic as well as personalized, strip lights can be cut and also stuck anywhere, according to job requirements.

Suspension fixture / Suspension Lamp / Suspension Light

Suspension fixture / Suspension Lamp / Suspension Light

Swing Arm Lamp

Adjustable folding arm lamp that can be utilized to provide job lights (lights up a specific location). Likewise described as a floating arm light or balanced arm light.


Task Lighting

Lighting components with the goal to improve visibility in a location where particular jobs will be executed, for this reason their name. The use of under closet lights for food preparation locations in cooking areas is an example of task lights.

Total Cost of Ownership (TCO)

Price of owning a lighting item over its whole lifetime. It includes the prices, installation expense, power consumption, maintenance, element substitutes and also deactivating cost.


A flooring light that uses a reflector on the top of a post to direct its whole output upward, which is then mirrored from the ceiling and walls.

Track Lighting

Illumination setup where a number of components are mounted on a typical track, which supplies them with power and enables each of them to be oriented in a different direction.

Translucent Material

A material that enables a partial transmission of light, usually diffusing it as well as eliminating glare. Frosted glass is an example of a translucent material.

Transparent Material

A material that permits most or every one of the light occurrences on it to travel through. Clear glass is a translucent product.


A recessed lighting component, made to be installed in an opening in the ceiling. Troffers commonly have predetermined dimensions, such as 2’x2′ or 2’x4′.

Twin Tube

A kind of CFL lamp where two parallel fluorescent tubes share the same base.


U-Bend Lamp

A sort of fluorescent light where television is curved in a U form, hence its name. U-bend lights normally have 2 bases, one on each end, which attach to various lampholders.

UL Label

A label put on by Underwriters Laboratories, which indicates an item has been tested for fire safety and security and electrical security.

Ultrasonic Sensor

An acoustic sensing unit that determines ranges by sending and also getting ultrasonic signals.

Ultraviolet Light

A type of electromagnetic radiation, undetectable to the human eye (i.e., past the visible spectrum) with a wavelength of 10 to 380 nanometers.

Under cabinet lighting

Set up under a cupboard or shelf, this lighting is utilized to produce localized lights and also can additionally act as a night light. It can come in LED, fluorescent, incandescent variations.

Universal Product Code

A 12-digit code found in lighting items, which can be checked at the point of sale.


Lighting approach where an item or surface is lit from below, with a luminaire that routes its output up. The applications of uplighting are normally decorative.


Valance Lighting

Illumination that is mounted over the top edge of home windows, where an opaque panel blocks direct vision of the component and the light is guided upward as well as downward because of this.

Vandal-Resistant Fixture

A lights fixture that is resistant to damaging or tampering, generally meant for outdoor public spaces.

Vanity Light

Lighting located above, beneath or on the side of a restroom mirror.

Vapor-Tight Fixture

A lighting fixture that is enclosed and gasketed to avoid the entrance of vapors or gases.


The electric potential difference between two contacts. Voltage drives electrical current via lighting fixtures and also other appliances, just like pressure drives the circulation of water in pipe installations.

Volumetric Troffer

A troffer that is specially designed for maximum optical performance, with a consistent light distribution that removes both glare and also the cavern result.


Wall Grazing

Illumination result where a wall surface with an irregular surface is brightened to ensure that there are both highlighted and shaded areas. This effect is only feasible on walls with granular surface areas, such as those constructed from rock or revealed brick. The opposite impact is wall washing.

Wall Sconce

See Sconce.

Wall Washing

Lighting effect where a wall surface is illuminated so that surface area abnormalities are reduced, it appears smoother. The contrary result is wall surface grazing.


Fully-encased luminaire that is created to be mounted on an outside wall to give area lights. Wallpacks are offered in HID, CFL as well as LED variations.

Warm White

White lights that are identified by a yellow shade. The term is normally utilized for lights with an associated shade temperature level (CCT) of around 3000K.


Measurement unit for the electric power consumption of illumination fixtures, or any other appliance that keeps up electricity. In lighting, lumens can be contrasted to miles traveled and watts can be contrasted to fuel consumption.

Watts to Lumens

To transform watts to lumens, multiply the power (P) in watts (W) with the luminous efficiency (η) in lumens per watt (lm/W).

Work Plane

The horizontal plane where activities are performed, generally 30 inches above the floor. Light designs are generally based on supplying a defined lighting level at the work plane.

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