LED Lighting Glossary

Accent Lighting

Accent lighting designed to highlight a particular object or area.

Ambient Light  

Ambient light is also sometimes called general lighting. It produces glare-free overall illumination.

Ampere (Amp)

Ampere is the measurement of electrical current in a circuit.

Current (Amps) = Power (Watts)/Voltage (Volts)


Used by some light fixtures to obtain the necessary conditions (voltage, current, wave form) to start and operate. For example, without a ballast to limit its current, a fluorescent lamp would almost immediately overheat and burn out.

Ballast Bypass  

Ballast bypass LEDs work straight off the line voltage flowing directly to the sockets, requiring you to remove the original ballast.

Beam Angle      

The beam angle is the angle at which the light is distributed.

Can light             

A can light is short for canister light and is a fixture installed in a hollow opening in a ceiling (also called recessed light or down light).

Candela (CD)    

A candela is the luminous intensity as defined by the international metric standard (SI). The term, retained from the early days of lighting, defines a standard candle of a fixed size and composition as a basis for evaluating the intensity of other light sources.


A manufacturer who places the CE marking on his/her product is declaring that the product conforms with EU safety, health or environmental standards; and complies with EU legislation. This marking permits the free movement of the product within the European market.

Color Rendering Index (CRI)      

The CRI is a measure of the quality of light, based upon a 0-100 scale. Natural light from the sun has a CRI of 100.  LED light CRI values generally range from 60 (average) to 90 (best). A high CRI equates to a sharper, crisper, more natural quality of light, while at the same time reducing glare.

Color Temperature        

Color temperature designates the color appearance of a light source measured in degrees Kelvin (K). The lower the temperature, the warmer the light appears. Warm white has a yellowish tint and falls in the range of 2000-3000K. Natural white lighting has a temperature of 3000-4000K. Cool white is typically 4500-6500K and has a bluish tint.

As a reference, incandescent lights generally have a low color temperature of about 2800K, while fluorescent tube lights typically have a color temperature of about 4100K.

Compact Fluorescent Lamp (CFL)            

A CFL is a fluorescent light bulb that has been compressed and sometimes twisted into the size of a standard-issue incandescent light bulb. CFLs are designed to replace an incandescent lamp or bulb and fit into most existing light fixtures formerly used for incandescent bulbs.  They have a similar life span and power consumption as LED bulbs. However, unlike LED bulbs, they also take several minutes to warm up and contain hazardous materials.


A controller is a device the controls the output of color-changing and dimmable light fixtures. It typically works together with a remote.

Cool white         

Cool white light has a color temperature range of 4550-7000K – usually perceived as slightly blue.


A diffuser is a device installed on a light fixture to improve uniformity and disperse light in a wider beam.


A diode is an electronic device that allows current to flow in one direction only.

Direct Light        

Direct lighting focuses the light directly onto a specified object or area.

Directional light source               

A directional light source emits a focused light beam in the direction it is oriented.


The DesignLights Consortium (DLC) is a group that concentrates specifically on energy efficiency in the commercial lighting industry. Manufacturers must have a DLC-approved third party test their products and must meet strict requirements to make the DLC’s Qualified Product list or to earn the DLC’s logo on their packaging.


Department of Energy


A driver is a device that converts incoming electricity to the appropriate and steady voltages needed by the LED chips, for example converting voltage from AC to DC. As more LED chips are added to the circuit, the driver increases its output voltage to maintain a constant current throughout all LED chips.

In LED lighting, the driver takes the place of a ballast. Drivers can be located inside the fixture/bulb or can be external as in the case of a strip lighting.


E26 is the U.S. standard base and E27 is the European standard base for light bulbs. The number after the E is the width of the base in millimeters.


The E39 base is also referred to as a mogul base.  This base is commonly found in street lights, high-wattage lamps and high intensity discharge bulbs. The number after the E is the width of the base in millimeters.


Intertek’s ETL Mark is proof of product compliance to North American safety standards. Authorities Having Jurisdiction (AHJs) and code officials across the US and Canada accept the ETL Listed Mark as proof of product compliance to published industry standards.

Flux/Luminous Flux       

Luminous flux is the measure of the total perceived power of light by the human eye.

Foot Candle      

A foot-candle is the amount of light produced one foot away from the source.


Hanalogen lamps are an advanced form of incandescent lamps, with a brighter color and longer life than the incandescent bulbs. They are commonly used in automotive headlamps, under-cabinet lighting, and work lights. In addition, hanalogen reflectors like MR and PAR lamps are often preferred for directed lighting such as spotlights and flood lights. One big disadvantage of hanalogen lamps is the large amount of heat they generate.

Heat sink            

A heat sink is the part of the thermal system that conducts heat away from sensitive components, such as LEDs and electronics.  The heat sink is then cooled by air circulated around it. Too much heat can damage the LEDs, resulting in lower light output, changes in color and decrease in life expectancy.


High-intensity discharge lamps (HID lamps) create light by producing an electric arc between two electrodes separated by an ionized gas. Examples of HID lamps include Mercury Vapor, High Pressure Sodium Vapor, and Metal Halide.

High Bay             

A high bay is a lighting system located high above the floor, typically in a an industrial setting.

High-Pressure Sodium (HPS)    

A high-pressure sodium lamp uses sodium in an excited state to produce light. It is very efficient and produces better color rendering than the LPS. It is the most common lamp for street lighting.

IES Files

IES files are photometric data files that are commonly used by lighting manufacturers to distribute photometric information about their products. IES stands for Illuminating Engineering Society.

Indirect Light    

Indirect lighting directs the light to bounce off of walls, ceiling, or reflectors to light the room.

IP rating              

The IP rating is two-digit number designating how well the light fixture is protected against solid bodies and dust, as well as moisture.

LED Bulb             

An LED light bulb is a finished product that is ready for use by the consumer with installed LEDs and electrical components.  An LED is not a bulb, but a bulb can contain LEDs.

LED Luminaire  

An LED luminaire is a light fixture complete with LED light emitting elements, housing, driver, and optical components to distribute light.

LED strips           

LED strips are usually printed circuit boards with LEDs soldered to the board. The strips can be rigid or flexible.

Light Emitting Diode (LED)          

An LED is a semiconductor device that emits light when an electric current passes through it. On its most basic level, the semiconductor is comprised of two regions. When voltage is applied and current begins to flow, the electrons move across one region into the other region. The process of an electron moving through the junction of the two regions releases energy. The dispersion of this energy produces light in the form of photons.

Low-Pressure Sodium (LPS)       

A low-pressure sodium lamp uses sodium in an excited state to produce light.  It is one of the most efficient types of lamp, however, it is not very popular due its poor color rendering.

Lumen (lm)       

A lumen is a measure of the total amount of visible light emitted by a light source. The higher the lumen rating, the brighter the light.


A luminaire is a fixture containing the light source.

Luminous efficiency      

Luminous efficiency is the percentage of light emitted from a source, taking into account light that is blocked or wasted. It is the most commonly used measure of the energy efficiency of a light source and usually expressed in lumens per watt (lm/w).


Lux measures the light intensity produced by a light fixture over a given area. It is measured in lumens per square meter.  In contrast to a lumen which measures light intensity in all directions from a light source, lux measures the intensity in a specific location from the source. Consequently, the lux measurement will decrease the farther away it is measured from the light source, but the lumen rating will remain the same.

Metal Halide    

A metal halide is a high-intensity discharge (HID) lamp that produces light by an electric arc through a gaseous mixture of vaporized mercury and metal halides. It is commonly used for overhead lighting in parking lots, sports arenas, factories, and retail stores.

Natural white   

Natural white light has a color temperature in the range of 3550-4500K.


The National Electrical Code (aka NFPA 70) is widely used throughout the U.S. to ensure safe electrical installations.


The National Electrical Manufacturers Association (NEMA) is the association of electrical equipment and medical imaging manufacturers.

Neon Lighting  

Neon lighting consists of brightly glowing, electrified glass tubes or bulbs. The color of the light depends on the type of gas in the tube/bulb. It is mainly used in neon signage for advertising.


Nationally Recognized Testing Laboratory


Optics determine the distribution of the LED chip’s light.


The Occupational Safety and Health Administration is a federal agency that regulates workplace safety and health.

Parabolic Aluminum Reflector (PAR)     

Parabolic refers to shape of the base, which is curved to catch and concentrate the light that is produced, as well as dissipate any heat produced by the LED. This unit is screwed or plugged into a type of housing, such as a can, tract light or some other fixture.  A number that stands for the diameter of the light typically follows PAR.


Used for dusk to dawn street lights and other light-sensitive applications, a photocell varies its resistance between its two terminals based on the amount of photons (light) it receives.


Photometry is the measurement of perceived light.

Plug and Play    

A plug-and-play LED lamp is a simple, one-for-one swap-out of the original linear fluorescent lamp. This lamp works directly with the existing fluorescent ballast, so there is no rewiring or ballast change required.

Pulse width modulation (PWM)              

PWM is also sometimes called pulse-duration modulation (PDM). PWM is the most common method used to dim LEDs. PWM allows you to change the proportion of time the signal is high compared to when it is low over a consistent time interval, thereby adjusting the brightness of LED lighting. It is similarly used to control RGB (red/green/blue) lighting. You can control how much of the three colors you want in the mix of color by dimming them by various amounts, thereby creating nearly limitless color variations.


RGB is a system whereby Red, Green and Blue light are combined in various proportions to obtain any color in the visible spectrum.  Levels of Red, Green, and Blue can each range from 0 to 100 percent of full intensity.

RGB White

RGB White is a method of producing white light by combining red, green and blue light.

RoHs Compliance           

The Restriction of Hazardous Substances (RoHs) specifies maximum levels for the following six restricted materials: Lead, mercury, cadmium, Hexavalent Chromium: (Cr VI), Polybrominated Biphenyls (PBB), Polybrominated Diphenyl Ethers (PBDE), Bis(2-Ethylhexyl) phthalate (DEHP), Benzyl butyl phthalate (BBP), Dibutyl phthalate (DBP) and Diisobutyl phthalate (DIBP).

Solid-state lighting (SSL)             

SSL is a lighting device that does not contain moving parts that can break, rupture, shatter, leak or contaminate the environment.

Surface Mount Device (SMD)    

An SMD is a low profile LED that is surface mounted to a printed circuit board.

TRIAC system   

The TRIode for Alternating Current (TRIAC) is a three terminal semiconductor device that can conduct current in either direction. It is commonly used in dimming systems.


A troffer is a long recessed light fixture that has historically been designed to house fluorescent lamps. However, it is now often designed with its own installed LEDs and electrical components.


UL is a global leader in testing, inspection, certification, auditing and validation. The UL Mark is one of the most accepted Certification Marks in the United States, appearing on 22 billion products annually.


Voltage is the rate at which energy is drawn from a source that produces a flow of electricity (amperage) in a circuit. The difference in electrical charge between two points in a circuit is expressed as volts.

Warm white     

Warm light has a color temperature in the range of 2500-3500K – usually perceived as slightly yellow.


A watt is the unit for measuring electrical power. It defines the rate of energy consumption by an electrical device when it is in operation. The energy cost of operating an electrical device is calculated as its wattage times the hours of use.