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We get it: you aren’t as into lights as we are. And that’s okay. We love light fixtures, lumens, CRI, beam angles, all of it. That’s our job. We won’t hold it against you that you don’t really care about those things. You just want to make sure you’re getting the best light for your illumination needs. One of the reasons we write this blog is so you can tackle your next project or replace your ageing bulbs with confidence. With that in mind we thought it would be helpful to put together a handy glossary of terms that you can reference if ever you have questions about what all the terminology means. We hope you find this useful!

• American National Standards Institute (ANSI) - facilitates the development of American National Standards (ANS) by accrediting the procedures of standards developing organizations (SDOs). These groups work cooperatively to develop voluntary national consensus standards. Accreditation by ANSI signifies that the procedures used by the standards body in connection with the development of American National Standards meet the Institute’s essential requirements for openness, balance, consensus and due process.
• Arc light - a lamp that produces light by an electric arc (also called a voltaic arc).The term is now used for gas discharge lamps, which produce light by an arc between metal electrodes through an inert gas in a glass bulb. The common fluorescent lamp is a low-pressure mercury arc lamp. The xenon arc lamp, which produces a high intensity white light, is now used in many of the applications which formerly used the carbon arc, such as movie projectors and searchlights.
• Baffle trim - a component of recessed or can lights that are manufactured with a ribbed interior, which offers minimum glare from the light bulb. The interior is further fitted with big uniform grooves which trap excess light. The softened light is more comfortable to the eyes. A dark-colored baffle trim will further reduce the glare and are often available in dark brown or black. This characteristic makes it perfect for rooms that do not need bright lights.
• Ballast - for use with fluorescent lights, the ballast regulates the current to the lamps and provides sufficient voltage to start the lamps. Without a ballast to limit its current, a fluorescent lamp connected directly to a high voltage power source would rapidly and uncontrollably increase its current draw. Within a second the lamp would overheat and burn out. During lamp starting, the ballast must briefly supply high voltage to establish an arc between the two lamp electrodes. Once the arc is established, the ballast quickly reduces the voltage and regulates the electric current to produce a steady light output.
• Bayonet connector - the standard light bulb fitting in the United Kingdom and in many countries that were members of the British Empire. It is a fastening mechanism consisting of a cylindrical male side with one or more radial pins, and a female receptor with matching L-shaped slot(s) and with spring(s) to keep the two parts locked together. The slots are shaped like a capital letter L with serif (a short upward segment at the end of the horizontal arm); the pin slides into the vertical arm of the L, rotates across the horizontal arm, then is pushed slightly upwards into the short vertical "serif" by the spring; the connector is no longer free to rotate unless pushed down against the spring until the pin is out of the "serif."
• Beam angle - the angle of light emitted from a lamp. The angle is measured between two directions for which the light intensity (candlepower) is 50 percent of maximum intensity. The wider the beam angle, the less intense the light. A PAR 38 has a relatively narrow beam angle, while an A19 has a wide angle.
• Beam spread - beam spread is the range of the surface illuminated, expressed in distance. To calculate beam spread, multiply beam angle by 0.18 by distance of surface from light source. Beam spread does not account for field spread – the outmost area illuminated by a light source.
• Bi-pin bases - A bipin or bi-pin (sometimes referred to as two-pin, bipin cap or bipin socket) is a type of lamp fitting. They are used on many small incandescent light bulbs (especially halogen lamps), and for starters on some types of fluorescent lights. Some sockets have pins placed closer together, preventing the low-power bulbs they use from being replaced by bulbs that are too high power, which may generate excessive heat and possibly cause a fire. These are sometimes called "mini-bipin." Where the terminals of the lamp are bent back onto the sides of the base of the bulb, this forms a wedge base, often used in small bulbs for automotive lighting.
• California Title 20 - legislation as of November 2019 stating that all GSLs must have an efficacy of 45 lumens per watt to be legally sold in California. That means almost all halogen and incandescent light bulbs will no longer meet the standards in California. Apart from a few exceptions, you'll only be able to buy CFLs and LEDs. Additionally, not all CFLs or LEDs are Title 20 compliant. Most of Sunlake’s LED bulbs do comply with the new statute.
• Can or canister light (see also “housing”) - a light fixture installed in a hole into a hollow opening in a ceiling. The can provides the main structure for the fixture and contains the socket or connection for the light itself. The main feature of the housing is designed to ensure that no flammable materials come into contact with the hot lighting fixture. Badly-housed downlights can be a fire hazard, though all newer ones contain a self-resetting thermal switch for safety.
• Candela - the unit of luminous intensity (candlepower) of a light source in a specific direction. One candela is approximately the same amount of light produced by an ordinary candle. When compared with lumens, candelas are a metric for the intensity of the light generated by a lamp.
• Candelabra base bulb - also known as the candle or torpedo bulb because of its shape, is made for an E12 or a C7 base. With an adapter, it can fit a standard socket (the screw in base).
• Color Rendering Index (CRI) - A scale from 0 - 100 percent which indicates how accurately a given light source (e.g. LED bulb) renders color when compared to a reference source (e.g. the sun). Most of Sunlake’s LEDs have a CRI of 80+ and some are rated 90+.
• Center Beam Candlepower (CBCP) - Center Beam Candlepower is the intensity of light at the center of a reflector lamp beam (expressed in candelas). This is an important measurement when you're aiming lighting in a specific direction, as it measures the concentration of the light to the center of the beam. Flashlights have a high CBCP while fluorescent tubes do not.
• Correlated Color Temperature (CCT) - Correlated color temperature (CCT or just color temperature) gauges how yellow or blue light appears. It’s measured in Kelvin and usually falls in a range between 2200 and 6500 Kelvin degrees. Warm light sources have low color temperatures (2200-3000K), featuring red, orange, and yellow colors. Cool light sources have high color temperatures (>4000K) and feature blue light.
• Compact Fluorescent Light (CFL) - a fluorescent lamp designed to replace an incandescent light bulb; some types fit into light fixtures designed for incandescent bulbs. The lamps use a tube which is curved or folded to fit into the space of an incandescent bulb, and a compact electronic ballast in the base of the lamp.
• Chromaticity - an objective specification of the quality of a color regardless of its luminance. Chromaticity consists of two independent parameters, often specified as hue (h) and colorfulness (s), where the latter is alternatively called saturation, chroma, intensity, or excitation purity. This number of parameters follows from trichromacy of vision of most humans, which is assumed by most models in color science.
• Current Limiting Resistors - a current limiting resistor is a resistor that is used to reduce the current in a circuit. You would usually want to have a current limiting resistor in series with your LED so that you can control the amount of current through the LED. If too much current is going through an LED, it will burn out too fast. If too little current is going through it, it might not be enough to light the LED.
• Damp-rated - designed to withstand moist environments, specifically those where condensation may build up in and around the fixture. Damp-rated lights can go both outdoors and indoors. They withstand moisture but not direct contact with the elements. You’ll see them in protected outdoor environments such as roofed porches, decks, sheds and basements.
• Delivered lumens (see also, “illuminance”) - defined as “light arriving at a surface, expressed in lumens per unit area." It is the general idea behind footcandles and lux. One lumen per square foot equals one footcandle, while one lumen per square meter equals one lux. Both of these units measure an area's illuminance, just as both miles and kilometers measure distance.
• DesignLights Consortium (DLC) - certification from this group signals a high level of both quality and energy efficiency. Unlike UL and ETL it is not a safety regulation.
• Dimmer - devices connected to a light fixture and used to lower the brightness of light. By changing the voltage waveform applied to the lamp, it is possible to lower the intensity of the light output. Although variable-voltage devices are used for various purposes, the term dimmer is generally reserved for those intended to control light output from resistive incandescent, halogen, CFLs LEDs. More specialized equipment is needed to dim fluorescent, mercury vapor, solid-state, and other arc lighting.
• Dusk to dawn LED - bulbs that come with either photocell and motion-activated capabilities. The photocell detects light and shuts off the bulb during the day, conserving energy. Some bulbs are coupled with motion sensor capabilities, shutting the light off during the day, turning it on at night, and increasing the brightness when motion is detected.
• E12 - the smaller “candelabra” base. Used for nightlight bulbs and sometimes for decorative light bulbs used in chandeliers and over bathroom mirrors.
• E26 - the most common light bulb base. It is used in most incandescent, halogen, CFL, CCFL, and HID light bulbs.
• Electrical Testing Labs (ETL) - electrical safety certification from Electrical Testing Labs, operated by Intertek. Required to pass inspections as building codes require products be either UL or ETL listed.
• Electrode - the structure that serves as the electric terminals at each end of an electric discharge lamp.
• Energy Star - the trusted, government-backed symbol for energy efficiency helping us all save money and protect the environment through energy-efficient products and practices. This certification typically means two things: the product is probably pretty reputable and trustworthy and the product is going to save you money on energy when compared with the conventional, run-of-the-mill, non-energy-efficient equivalent of that product.
• Eyeball trim - recessed lighting that can be directed toward a specific place. When regressed, they point downward without protruding from the fixture.
• Filament - the part of a traditional light bulb that incandesces or glows when electricity is run through it.
• Fixture (see also “luminaire”) - a complete lighting unit consisting of a lamp or lamps and the parts designed to distribute the light, to position and protect the lamp(s), and to connect the lamp(s) to the power supply.
• Fluorescent light - a glass tube which radiates light when phosphor on its inside surface is made to fluoresce by ultraviolet radiation from mercury vapor.
• Footcandle - a unit of illuminance equal to 1 lumen per square foot of surface. Really, footcandles are an indirect measure of delivered lumens. If a lighting product can put out 1,000 lumens, the number of those lumens that actually arrive at a particular square foot of space to illuminate it can be quantified by footcandles.
• General Service Lamp (GSL) - a classification for lights including general service incandescent lamps (GSILs), compact fluorescent lamps (CFLs), general service light-emitting diode (LED) lamps, organic light-emitting diode (OLED) lamps, and any other lamps that are used to satisfy lighting applications traditionally served by GSILs. GSLs are used in general lighting applications and account for the majority of installed lighting in the residential sector.
• Gimbal trim - Similar to eyeball trim lighting, they can be positioned to illuminate a specific place, however the lamp doesn’t extend out of the housing, when fully pivoted the trim will block some of the light.
• Halogen - technically an incandescent light bulb. illumination is produced in both when a tungsten filament is heated sufficiently to emit light or "incandescence." Halogen is the name given to a family of electronegative elements, including bromine, chlorine, fluorine and iodine. Halogen bulbs are referred to variously as "tungsten halogen," "quartz halogen," or simply "halogen."
• High Intensity Discharge (HID) - an electrical gas-discharge lamp which produces light by means of an electric arc between tungsten electrodes housed inside a translucent or transparent fused quartz or fused alumina arc tube. These are commonly used as vehicle headlights due to their compact size and the intensity of their light output
• Housing (see also “can”) - a light fixture installed in a hole into a hollow opening in a ceiling. The can provides the main structure for the fixture and contains the socket or connection for the light itself. The main feature of the housing is designed to ensure that no flammable materials come into contact with the hot lighting fixture. Badly-housed downlights can be a fire hazard, though all newer ones contain a self-resetting thermal switch for safety.
• Illuminance (see also “delivered lumens”) - defined as “light arriving at a surface, expressed in lumens per unit area." It is the general idea behind footcandles and lux. One lumen per square foot equals one footcandle, while one lumen per square meter equals one lux. Both of these units measure an area's illuminance, just as both miles and kilometers measure distance.
• Incandescent light - an electric light with a wire filament heated until it glows. The filament is enclosed in a bulb to protect the filament from oxidation. Current is supplied to the filament by terminals or wires embedded in the glass. A bulb socket provides mechanical support and electrical connections.
• Indirect light - lighting in which the light emitted by a source is diffusely reflected (as by the ceiling).
• Insulation contact (IC) - a rating system for recessed lights to ensure lights won’t overheat and cause a fire when in contact with insulation or other flammable materials in the ceiling.
• Light Emitting Diode (LED) - a semiconductor light source that emits light when current flows through it. Electrons in the semiconductor recombine with electron holes, releasing energy in the form of photons. The color of the light (corresponding to the energy of the photons) is determined by the energy required for electrons to cross the band gap of the semiconductor. White light is obtained by using multiple semiconductors or a layer of light-emitting phosphor on the semiconductor device.
• Luminosity - an absolute measure of radiated electromagnetic power (light), the radiant power emitted by a light-emitting object. It is measured in joules per second, or watts.
• Lumen per watt (LPW) - a measurement of luminous efficacy, or how well a light source produces visible light. It is the ratio of luminous flux to power.
• Lumens - a measure of the total quantity of visible light emitted by a source per unit of time. Luminous flux differs from power (radiant flux) in that radiant flux includes all electromagnetic waves emitted, while luminous flux is weighted according to a model (a "luminosity function") of the human eye's sensitivity to various wavelengths. Lumens are related to lux in that one lux is one lumen per square meter.
• Luminaire (see also “fixture”) - a complete lighting unit consisting of a lamp or lamps and the parts designed to distribute the light, to position and protect the lamp(s), and to connect the lamp(s) to the power supply.
• Lux - a measurement of lumens over a square meter rather than over a square foot (footcandles). A lux is equal to 1 lumen per square meter of surface. Footcandles are to the imperial system what lux are to the metric system.
• Mercury - poisonous heavy metal found in fluorescent light bulbs. As a result CFLs and traditional fluorescent bulbs require special handling and disposal.
• Metal halide - an electrical lamp that produces light by an electric arc through a gaseous mixture of vaporized mercury and metal halides (compounds of metals with bromine or iodine). It is a type of high-intensity discharge (HID) gas discharge lamp. They are used for general lighting purposes both indoors and outdoors, such as commercial, industrial, and public spaces, parking lots, sports arenas, factories, and retail stores, as well as residential security lighting; automotive and specialty applications are further fields of usage.
• Panel light - designed for both residential and commercial applications. This type of lighting fixture is made to replace conventional fluorescent ceiling lights, and designed to mount on suspended grid ceilings or recessed ceilings. LED panel lighting delivers a smooth and flawless wall of illumination without visible bulbs or hot spots. Their versatility allows them to be mounted on numerous surfaces and used in multiple applications.
• Pendant light fixtures - sometimes called a drop or suspender, is a lone light fixture that hangs from the ceiling usually suspended by a cord, chain, or metal rod.
• Photon - a type of elementary particle. It is the quantum of the electromagnetic field including electromagnetic radiation such as light and radio waves, and the force carrier for the electromagnetic force. Simply put, a photon is an individual particle of energy that is light.
• Recessed lighting - Recessed lighting is installed directly inside a ceiling, wall, or other surface. Recessed fixtures consist of three main components, housing, trim, and bulb. Housing is the bulk of the fixture which is hidden within the wall or ceiling and contains the electrical connections of the fixture. Trim is the decorative, visible portion of the fixture and may include baffles, reflectors or shades. The final component is the bulb, the part of the fixture that produces light.
• Retrofit - the addition of new technology or features to older systems, for example, installing new, energy-efficient LED lights in fixtures manufactured before LEDs were a viable alternative to incandescent or fluorescent bulbs.
• Sconce - a type of light fixture that is fixed to a wall. The light is usually, but not always, directed upwards and outwards, rather than down. The sconce is a very old form of fixture, historically used with candles and oil lamps. Modern fittings are more often called wall lights or similar terms, especially if the light source is wholly covered by glass. They can provide general room lighting, and are common in hallways and corridors, but they may be mostly decorative. A sconce may be a traditional torch, candle or gas light, or a modern electric light source affixed in the same way.
• Screw bases - Screw-base bulbs, often called Edison bulbs, are named after their inventor, Thomas Edison. In North America and Europe, these light bulb base types are the most common and widely used. Each base type has a descriptive term, such as medium, intermediate, candelabra, etc., and they’re defined by the letter E (Edison) followed by numbers. The numbers refer to base width either in eighths of an inch or in millimeters.
• Smart lights - a lighting technology designed for energy efficiency. This may include high efficiency fixtures and automated controls that make adjustments based on conditions such as occupancy or daylight availability. Smart lights are often WiFi enabled and can be programmed through an app on a smartphone.
• Smooth or open trim - In contrast to baffle and reflector trims, smooth or open trims are a simple ring flush around the lamp, exposing as much light as possible to the environment. Available in an assortment of colors as well, these are an economical choice.
• Socket - an electrical device receiving a plug or light bulb to make a connection.
• Spotlight - a lamp projecting a narrow, intense beam of light directly on to a place. When used in residential lighting, most commonly used in conjunction with a recessed lighting fixture or as an exterior light.
• Track lights - a method of lighting where light fixtures are attached anywhere on a continuous track device which contains electrical conductors. This is in contrast to directly routing electrical wiring to individual light positions. Tracks can either be mounted to ceilings or walls, lengthwise down beams, or crosswise across rafters or joists. They can also be hung with rods from especially high places like vaulted ceilings.
• Twist and lock bulbs / bases - bulbs have two pins protruding from the base instead of the usual screw-in base. To install the bulb, insert the pins into the corresponding holes in the socket and twist the light bulb to lock it into place.
• Underwriter Laboratory (UL) - signifies that a lighting product has passed UL’s safety requirements for use by consumers and in places of business. Required to pass inspections as building codes require products be either UL or ETL listed.
• Ultraviolet (UV) - a form of radiation which is not visible to the human eye. It's in an invisible part of the electromagnetic spectrum. There are different kinds of UV light.
• UVC light - UVC refers to ultraviolet light with wavelengths between 200 – 280 nanometers (nm). Light in the UVC wavelength can be used for disinfecting water, sterilizing surfaces, destroying harmful microorganisms in food products and in air. It can also cause damage to human skin and eyes and should be used carefully.
• Voltage - electric potential difference, electric pressure or electric tension is the difference in electric potential between two points. The difference in electric potential between two points (i.e., voltage) in a static electric field is defined as the work needed per unit of charge to move a test charge between the two points. Most residential appliances use 120 volt power, while some larger appliances like washers, dryers, and refrigerators may use 220 volt power.
• Wall pack - exterior building lights are terms that describe the outdoor lighting that is commonly mounted on the outside facing walls of buildings. This type of exterior lighting is generally used to provide illumination to ground areas frequented by vehicles and pedestrians. They also function well as an added layer of security for property owners. It is not uncommon to see multiple fixtures mounted on a single building or wall, with the fixture spacing designed to provide even lighting around the grounds.
• Watt - a unit of power. In the International System of Units (SI) it is defined as a derived unit of 1 joule per second, and is used to quantify the rate of energy transfer. Basically, it’s a way to quantify the amount of energy consumed over a period of time.
• Wattage equivalence - a reference to the energy consumption between incandescent lights and LEDs. LEDs can produce the same amount of light as an incandescent by consuming much less energy. A 60W incandescent bulb uses 60 joules of energy per second to produce light whereas a “60W” LED uses 9W to produce the same amount of light.
• Wet-rated - used in places with direct exposure to water. These locations include almost all outdoor lights, including landscape lighting such as path lights and ground wells. Fixtures rated for wet locations use waterproof seals to protect their internal components from moisture. This eliminates leaks and allows them to safely function in places where other fixtures would fail.
• Xenon - a highly specialized type of gas discharge lamp, an electric light that produces light by passing electricity through ionized xenon gas at high pressure. It produces a bright white light that closely mimics natural sunlight, with applications in movie projectors in theaters, in searchlights, and for specialized uses in industry and research to simulate sunlight, often for product testing. Xenon headlamps in automobiles are actually metal-halide lamps, where a xenon arc is only used during start-up to correct the color temperature.