Absorption of Light / Absorptance Refers to a measure of the amount of light absorbed by an object, instead of being reflected.
and matte surfaces are the least likely to reflect light.
Accent Light 1) Illumination used to make something stand out. It may be done with intensity and/or
2) A luminaire that provides such illumination.
Acrylic Acrylic is a plastic manufactured using one or more derivatives of acrylic acid. Polymethyl
acrylic is one of the more widely used forms of acrylic due to its exceptional weatherability,
clarity and versatility. Transparent, translucent opaque and colored polymers are available with
levels of heat resistance, light transmissions, impact strength, flow rates and release
PMMA acrylic sheet exhibits glass-like qualities – clarity, brilliance, transparency, translucence –
at half the weight with up to 10 times the impact resistance. It can be tinted or colored, mirrored
made opaque. A number of coatings can be applied to a sheet or finished part for performance
characteristics such as scratch resistance, anti-fogging, glare reduction and solar reflectivity.
ALA American Lighting Association, a trade association that encompasses the USA, Canada and the
focusing on residential lighting. ALA members include manufacturers, event organizers and designers.
Albedo Also known as Reflectance, it is the ratio of incident luminous flux upon a surface which is
in the visual spectrum.
Ambient Light The general lighting present in an area, excluding task lighting and accent lighting but
lighting and daylight streaming in.
Amp Calculations Formula: Amps = watts ÷ volts
Amperage (A) The amount of electrical current through a conductive source.
Ampere (A) A unit of measurement for Electrical Current.
Angle of Light Angle between the orientation of a light source and the viewing direction. For example, the
light is 0° when looking at a downlight directly from below, and increases progressively as the
steps away from it. The term is commonly used in theatrical lighting, to describe the angle between
stage lighting direction and the viewer’s line of sight.
Application The intended use of a lighting product. Residential, retail, hospitality, healthcare and
are all examples of lighting applications.
Arc Lamp Any lamp that establishes an electric arc between two electrodes. Arc lamps generally stimulate
making it glow and generating a lighting output.
Decorative lighting that is part of a building’s design and construction. It also provides
lighting as a secondary function.
Art Deco Art Deco is a design style that evolved from the Art Nouveau, which was popular during the 1920s
1930s. Art Deco is also one of the most well known interior design styles and stood for modernity as
well as elegance and glamour. It is noted for clean lines, bold colour, angular shapes, and stylized
patterns such as zig-zags. Lavish ornaments were also used to give an extra sense of glamour.
Back Plate The part of a fixture that mounts to a wall or vertical surface.
Backlight The lighting output of outdoor fixtures that is emitted opposite to the intended direction,
an undesirable effect. For example, if the pole lamps in a parking lot emit backlight towards
homes or apartments, it can be bothersome for the property owners.
Backlight should not to be confused with backlighting, an accent lighting technique.
Backlighting Lighting designed to illuminate an object from behind, which causes an appealing glow effect
edges. Backlighting is a type of accent lighting, and is commonly used to draw attention to works of
Backlighting should not to be confused with backlight, an undesirable lighting effect that can
by outdoor fixtures.
Baffle An opaque or translucent component that blocks direct sight of a lighting source.
Ballast Used in light sources such as fluorescent and high intensity discharge (HID) lamps, this
of equipment is required to start and control the flow of current for the gas discharge.
Ballast Factor This is the percentage of a lamp's rated lumen output that can be expected when operated on a
commercially available ballast. A ballast with a lower BF results in less light output and also
consumes less power.
Base The base is the end of the lamp that fits into the socket. There are many types of bases used in
screw bases being the most common for incandescent and HID lamps, while bipin bases are common for
Base Temperature Maximum allowable temperature of a lamp base, which must be considered when designing the
Beam LumensThe total lumens present within the portion of the beam contained in the beam angle.
Beam Spread The Beam Spread is a general term, describing the angle between the two directions opposed to
over the beam axis for which the luminous intensity is a certain fraction of that of the maximum
intensity. The amount of that fraction needs to be given in each specific case.
Binning In the industrial fabrication of LED chips, variations always occur: the light-emitting
for example in terms of colour and illuminance. The LEDs are sorted ensure a consistent light
with a uniform brightness level and light colour. They are separated into bins. This binning process
is particularly important for white LEDs.
Bollard A short, thick post with a light at its top, used for grounds and outdoor walkway lighting.
BUG Rating BUG is an acronym for backlight, uplight and glare, and the term was developed by the
Society (IES) and International Dark-Sky Association (IDA) to describe the amount of light emitted
a fixture in unwanted directions.
- Backlight is directed behind the luminaire.
- Uplight is directed upwards.
- Glare causes a visual impairment.
In the BUG rating, these effects are indicated in a scale from 0 to 5, where 0 indicates the
minimized and 5 indicates it is not controlled at all. Therefore, the best possible BUG rating is B0
U0 G0, and the worst possible rating is B5 U5 G5.
Bulb 1) The source of electric light. To be distinguished from the whole assembly. Lamp often is used
the bulb and its housing.
2) The glass part of the lamp. Lamps are produced with a variety of bulb shapes. LED light
not utilize a bulb.
3) A loose way of referring to a lamp. "Bulb" refers to the outer glass bulb containing the
Burn Position The operating position for which a lamp is designed. For example, some lamps can only operate in
base-up position. Lamps operating in positions for which they are not designed generally suffer
performance or short-term failure.
Can Common term for the housing of a recessed downlight.
Candela (cd) The measure of luminous intensity of a light source in a given direction. The term has been
from the early days of lighting when a standard candle of a fixed size and composition was defined
producing one candela in every direction. A plot of intensity versus direction is called a candela
curve and is often provided for reflectorized lamps and for luminaires with a lamp operating in
Candlepower (cp) Luminous intensity expressed in candelas.
Canopy Mounting The decorative plate that attaches to the ceiling to cover the junction box.
Cave Effect An effect that occurs when lighting fixtures direct all of their lighting downward and little or
is reflected back up towards the ceiling or upper wall portions. The cave effect is generally
because it makes indoor spaces feel ominous, like the interior of a cavern.
Ceiling Cavity The portion of a room that is above the lighting fixtures.
Ceiling Light There are two basic types of ceiling light: Flush mounts are ceiling lights that attach to the
with little to no gap between the light fixture and the ceiling. Semi-flush area ceiling light that
to the ceiling with a stem or part that creates a gap between the ceiling and the light.
Chandelier A multi-arm, decorative, often ornate ceiling light fixture that holds a number of bulbs.
CIE International Lighting Commission (French: Commission internationale de l’éclairage), an
organization in the lighting industry across the globe.
Circuit Breaker Electrical protection device that is normally located within a distribution board. Each lighting
is connected to a circuit breaker, and it interrupts current automatically if an overload or fault
Coefficient of Utilization (CU) The fraction of a lamp’s luminous output that reaches the work plane. The CU is influenced by
efficiency of the fixture, as well as room geometry and colors.
Color Render Index (CRI) An international system used to rate a lamp's ability to render object colours. The higher the
upon a 0-100 scale) the richer colours generally appear. CRI ratings of various lamps may be
but a numerical comparison is only valid if the lamps are close in colour temperature. CRI
among lamps are not usually significant (visible to the eye) unless the difference is more than 3-5
Compact Fluorescent Lamps (CFLs) The general term applied to fluorescent lamps that are single-ended and that have smaller
that are bent to form a compact shape. Some CFLs have integral ballasts and medium or candelabra
bases for easy replacement of incandescent lamps.
Correlated Color Temperature (CCT) Unlike the CRI, which describes how faithfully a light source represents other objects, the
color temperature (CCT) describes the color output of the lamp itself. Some common CCT values
- 2700K, with a warm tinge of yellow that creates appealing and relaxing environments
- 4000K, a neutral white tone that strikes just the right balance between relaxation and
- 6500K, with a slight tinge of blue, which has an energizing effect
Although the correct technical term is correlated color temperature, it is often shortened to
temperature. It is also important to note that the CCT is not the real operating temperature of a
- it is the temperature to which you would have to heat a black body to make it glow with the same
For example, an LED bulb with a CCT of 5000K glows in the same color as a black body heated to a
temperature of 5000K, but the LED bulb itself does not reach that temperature.
Cove Lighting A type of lighting that generally directs it output towards the ceiling, and where individual
are hidden in ledges. Cove lighting is often used for decorative purposes because it can emphasize
borders of walls, as well as ceiling features.
Current (l) A measure of the rate of flow of electricity, expressed in amperes (A).
Cutoff Angle Viewing angle beyond with it is no longer possible to see a light source directly, measured from
direction exactly below the lamp.
Desk Lamp A compact fixture used for task lighting on a desk, and which is generally portable.
Diffused Light Light produced by an extended surface, either directly or through reflection. Diffused light
a uniform and soft distribution that minimizes shadows.
Diffused Light Light produced by an extended surface, either directly or through reflection. Diffused light
a uniform and soft distribution that minimizes shadows.
Dim 1) To change the intensity of a luminaire.
2) The state of a luminaire at very low intensity.
Dimmable Adjective used to describe a lamp or fixture whose lighting output can be modulated with a
Dimmer 1) An apparatus used to control the intensity of a luminaire.
2) A device used to lower the light output of a source, usually by reducing the wattage it is
operated at. Dimming controls are increasing in popularity as energy conserving devices.
Direct / Indirect Lighting Lighting that is mixed from direct sources and indirect reflection. In electrical lighting,
of different types are installed, or there are luminaires that emit light both up to the ceiling and
down to the workspace.
Direct Lighting Light produced by point surfaces, which results in a concentrated output that accentuates edges
Directed light normally causes glare when the sources is viewed directly.
Downlight A compact lighting fixture that directs its output downward, allowing no upward emission of
can be recessed, surface-mounted or pendant.
Driver Piece of electronic equipment that transforms the main supply voltage into a lower DC voltage
appropriate for LED lighting. Some LED lamps have a built-in driver, while others require one to be
externally, just like the ballasts used by fluorescent and HID lamps.
Efficacy Describes how effectively a lighting fixture can convert electric power into lighting, measured
per watt. This is like the gas mileage of a sports car, where the lighting output can be compared to
miles traveled, and the electric power input is like fuel consumption.
Efficiency Conversion ratio between lighting power output and electric power input, measuring both
watts. Not to be confused with efficacy, which describes the ratio between lumen output and watts
Since lumens describe lighting output better than watts, efficacy tends to be a much more useful
in lighting design.
Emergency Lighting Lighting designed to provide visibility when the normal lighting system fails, for example
Emergency lighting is equipped with batteries, allowing it to operate long enough for a building to
Energy Star An energy savings and sustainability program by the US Department of Energy and Environmental
Agency. Lighting products with the ENERGY STAR have been tested for superior energy efficiency.
Filament The wire coil that is heated to produce lighting in incandescent and halogen lamps, normally
Fixture A term that is often used interchangeably with Luminaire. The assembly that holds the lamp in a
system. It includes the elements designed to give light output control, such as a reflector (mirror)
or refractor (lens), the ballast, housing, and the attachment parts.
Floodlight High-power lighting fixtures that typically use HID bulbs or their LED equivalents. They are
used outdoors to emphasize specific objects or areas.
Floor Lamp An electric light supported by a tall pole that is attached to a base that rests on the floor of
Fluorescent Lamp One of the main types of lighting, far more efficient than incandescent and halogen bulbs, but
by LED lighting. A fluorescent lamp uses electrodes to stimulate mercury vapor and produce
(UV) radiation, which in turn stimulates the phosphor coating of the lamp to produce visible light.
Foot Candle (fc) Measurement unit for illuminance, or lumens per unit of area. One foot-candle is equivalent to
per square foot.
Frosted Lens A white lens that is translucent but not transparent, which diffuses the output of a lamp.
Glare Visual impairment caused by a bright source of light, directly visible or reflected by a
are two types of glare:
- Discomfort glare causes an instinctive reaction to close the eyes and look away. This is the
glare felt when exposed to a potent HID light or when the sun is directly visible through a window.
- Disability glare impairs vision, but does not cause the same reaction as discomfort glare. If
source gets reflected on your laptop screen, for example, it does not bother your eyes but
objects on the screen may be impossible.
Halogen A type of incandescent lighting in which the filament burns hotter and longer, producing a
that typically lasts longer than standard incandescent.
Hard Light A light source that creates shadows with a very sharp edge when cast on objects. Direct lighting
a concentrated source is generally hard light, and some examples are:
- The sun in a day with clear skies.
- A camera flash.
- Highly directional lighting fixtures such as floodlights and spotlights.
HID Acronym for high-intensity discharge, a type of lighting often used for industrial and outdoor
due to its powerful output. Some examples of HID lighting are mercury-vapor, metal-halide, xenon,
sodium and low-pressure sodium lamps.
All types of HID lamps produce lighting by stimulating an enclosed gas with an electric arc, and
they operate at high temperatures.
High-Bay Lighting Lighting systems designed for ceiling heights of 25’ or more, commonly found in sports
or industrial locations.
High-Output (HO) Lamp Fluorescent tubes with a higher lumen output and rated power than conventional fluorescent
example, a normal 48” T5 tube may consume 28 watts and provide 2400 lumens, while an HO version may
54 watts and provide 5000 lumens.
IALD International Association of Lighting Designers, a global association that promotes best
lighting design, while providing training and scholarships.
Illuminance The luminous flux on a surface, per unit of area. The illuminance requirements of built
are determined by their intended purpose, and there are two common units of measurement:
- Lux - Equivalent to one lumen per square meter.
- Foot-candle - Equivalent to one lumen per square foot.
Higher illuminance levels make surfaces appear brighter to the human eye and improve visibility.
Illuminati Italian word meaning "to illuminate", light, or brighten.
Illuminating Engineering Society of North America (IES or IESNA) The professional society of lighting engineers, including those from manufacturing companies,
professionally involved in lighting.
Incandescent Lamp A type of lamp with a tungsten filament that glows when it carries current. Incandescent
a perfect color-rendering index of 100, comparable to that of the sun, but is among the least
types of lighting.
Indirect Lighting Lighting provided by reflection usually from wall or ceiling surfaces. In electrical lighting,
are suspended from the ceiling or wall mounted and distribute light mainly upwards so it gets
off the ceiling or the walls.
Instant Start Ballast A type of fluorescent lighting ballast that applies a high-voltage pulse to the lamp, making it
instantly without preheating the electrodes. The drawback of instant-start ballasts is that they
the service life of lamps: electrode material is expelled each time the lamp is started, blackening
edges and causing eventual failure.
Integrated Lighting Fixture geometry. Integrated lighting fixtures are generally more efficient than lamp-based LED
they make retrofits more expensive because the entire fixture must be replaced, not only the lamps
IP Rating Ingress Protection rating, a two-digit code that indicates the resistance of a lighting fixture
particles and liquids, where higher digits indicate enhanced protection. The first digit indicates
against solids, and the second indicates the protection degree against liquids.
For example, an IP67 rating indicates a higher degree of protection than an IP54 rating.
Junction Box An enclosure that houses electric wires or cables that are joined together and protects the
Junction boxes are also sometimes called "gang boxes" or "splitter boxes."
Kelvin Scale 1) The common unit of measure for the colour temperature of a light source.
2) Kelvin is used to indicate the overall colour of the light produced from a source.
Kilowatt (kW) Measurement unit for electric power, equivalent to 1000 watts. This term should not be confused
Kilowatt-hour (kWh) Measurement unit for energy consumption. As implied by its name, it is equivalent to the amount
consumed by a one-kilowatt appliance running for one hour. Electric utility bills are often
based on kilowatt-hour consumption per month. This term should not be confused with kilowatt.
Lamp Life The average lifespan for a specific type of lamp.
Lamp Lumen Output This value indicates the lumen output (or luminous flux) irradiated by the luminaire or LED.
Lamp Power The lamp power is specified in watts and indicates only how much energy the individual lamp or
Landscape Lighting Landscape lighting can extend the use of outdoor space while providing safety, atmosphere, and
definition. Lighting can also accent areas of a landscape or create patterns and contrast.
use of a landscape requires good visibility. It is not essential to highly illuminate all areas, but
highlight specific areas like steps, entry areas, and walkways to eliminate shadows and dark spots.
Layering Light An interior design approach where several types of lighting are combined to achieve a specific
LED / Light Emitting Diode Acronym for light-emitting diode, a solid-state component that emits light when exposed to
LED lighting represents the state-of-the-art in the industry, outclassing most other types of
in terms of energy efficiency, design flexibility and colors of light available.
LED Average Life Unlike other light sources, LEDs usually don’t “burn out”. Instead, they get progressively
what is called lumen depreciation. LED useful life is typically based on the number of operating
until the LED is emitting 70 percent of its initial light output.
Lens Lamp or luminaire component that has the goal of dispersing the lighting output so that the
pattern is achieved.
Light Loss Factor (LLF) A factor used in lighting design to account of the degradation in luminous output over time. The
accounts for many aspects such as reflector or lens degradation, dust accumulation, lamp degradation
due to voltage surges or heat, etc.
For example, if the LLF is 0.80 and a room needs 40,000 lumens, the lighting system will be
to provide 50,000 initial lumens (50,000 lm x 0.80 = 40,000 lm).
Light Pollution Light that is directed to areas where it is not needed, and thereby interferes with some visual
Light pollution directed or reflected into the sky creates a "dome" of wasted light and makes it
to see stars above cities.
Light Quality Every source has five main attributes that affect the quality of light emitted and the overall
1) Hard or Soft (or in between);
2) Intensity (the amount of light);
3) Direction (in relation to the lens/subject axis);
4) Colour (of light emitted); and
5) Beam pattern (the Beam Angle, shape, and any shadow patterns).
All but colour are affected by the light's Size and Distance, which may also be considered
Louver A translucent or opaque screen that blocks direct visibility of a light source and eliminates
Lumens A measure of luminous flux or the total “amount” of visible light emitted by a source.
Luminaire A complete lighting unit consisting of a lamp (or lamps), ballast (or ballasts) as required
with the parts designed to distribute the light, position and protect the lamps and connect them to
power supply. A luminaire is often referred to as a fixture.
Luminaire Efficiency The ratio between the lumens emitted by a complete luminaire to those emitted by the lamps
portion of lighting is always lost due to internal geometric features and reflection.
Luminous Flux Total output emitted by a light source, measured in lumens. The luminous flux describes the
output of a lighting fixture without considering direction.
Luminous Intensity Lighting emission in a specific direction, measured in candelas. Luminous intensity changes
on the viewing angle.
Lux Measurement unit for illuminance, or lumens per unit of area. One lux is equivalent to one lumen
A key component of lighting designed is achieving a suitable illuminance level depending on the
Matte A way of describing the surface of an object as dull or without lustre.
Medium Base Also known as E26 or standard base, it is the screw-shaped base used by most residential light
Metal Halide (MH) A subtype of HID lamp that produces its lighting output by stimulating vaporized metal-halide
compounds, hence its name. Like mercury lamps, MH lamps are commonly used in outdoor and industrial
Ceramic metal halide is a subtype of MH lamp, where the arc tube is made from a ceramic material
instead of quartz glass. This improves the color rendering index of the lamp.
Metallization Metallization is the general name for the technique of coating metal on the surface of objects.
Metallic coatings may be decorative, protective or functional. Techniques for metallization started
as early as mirror-making.
Mounting Height Depending on the application, mounting height can have two possible definitions:
- Distance between the bottom of the fixture and the work plane.
- Distance between the bottom of the fixture and the ground.
MR Lamp MR is an acronym for multifaceted reflector, a component used to shape the output of a light
into a directional beam. MR lamps typically use incandescent, halogen or HID bulbs, and there are
also LED replacements available. MR lamps are available with both screw bases and pin bases.
The MR designation is followed by a numerical value indicating the lamp diameter in 1/8ths of an
inch, where two of the most common types are MR11 and MR16.
Natural Light Nature's illumination: daylight, even on interiors. The term implies that the source is not
Occupancy Sensor A device that uses infrared or ultrasonic radiation, or sound, to detect the presence of humans
and switch the lights accordingly. Occupancy sensors are an effective energy-saving measure.
OLED / Organic Light Emitting Diode An organic light-emitting diode (OLED) is a light-emitting diode (LED) in which the emissive
electroluminescent layer is a film of organic compound that emits light in response to an electric
current. This layer of organic semiconductor is situated between two electrodes; typically, at least
one of these electrodes is transparent. OLEDs are used to create digital displays in devices such as
television screens, computer monitors, portable systems, and lighting fixtures.
Opaque Material A material that completely blocks visible light.
Optic The components of a luminaire such as reflectors, refractors, protectors which make up the light
Pendant A pendant light, 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. Pendant lights are often used in
multiples, hung in a straight line over kitchen countertops and dinette sets or sometimes in
bathrooms. Pendants come in a huge variety of sizes and vary in materials from metal to glass or
concrete and plastic.
Photometry The measurement of light and its properties.
Power Factor (PF) Ratio of real power to apparent power drawn by lighting fixtures and other electrical devices.
The real power is represented by the actual watts consumed, while the apparent power is the
multiplication product of voltage and current, measured in volt-amperes. Electric utility companies
normally apply additional charges if the power factor of a building drops below a specified level.
Programmed Start Ballast A ballast that preheats the electrodes of a fluorescent lamp before igniting it, which reduces
their wear over time and extends the service life of the lamp. Preheating is accomplished by
applying a very low voltage that is high enough to raise the temperature of electrodes, but without
causing the lamp to ignite.
Pulse Start Ballast A type of ballast used with HID lighting, which uses a series of controlled voltage pulses to
ignite the lamp, minimizing damage to the electrodes each time the lamp is turned on.
Quick Ship Items that are typically in stock, that are readily available to be shipped within 1-2 weeks.
Radiant Flux The output of a light source in radiant energy weighted by the spectral response curve of the
human eye per time unit. Standard unit for radiant flux is Watt (W).
Rapid Start Ballast A type of ballast for fluorescent lamps, which preheats the electrodes and applies voltage
simultaneously. This type of ballast is faster than an programmed start ballast, but slower than an
instant start ballast. The resulting electrode damage when the lamp is started is intermediate
between that of instant start ballast (high damage) and programmed start ballast (low damage), and
the resulting service life is also intermediate as a result.
Recessed Lighting Recessed lighting refers to fixtures that are set into ceilings or walls. Commonly called cans
because of their shape, they include the housing (the internal part in the ceiling that you don't
see) and the trim, which is visible. With little or no profile, recessed lighting provides effective
ambient and accent illumination for both residential and commercial use.
Reflector An internal component of many lamps and luminaires. It has a reflective surface and its geometry
is specially designed to provide a specific lighting distribution. Reflectors are often used with
lamps that emit light rays in every direction (HID, fluorescent, etc.) to concentrate their output
in a specific direction.
Restrike Time Time required by an HID lamp to achieve full brightness after it has been turned off.
Retrofit A lighting system upgrade, generally with the goal of improving energy efficiency and site
Saturation The resulting “colorfulness” when objects are exposed to a light source, compared to that
resulting from natural lighting. If the colors appear more intense, the light source saturates them;
on the other hand, if colors are dulled, the light source desaturates them.
Sconce A decorative lighting fixture with a flat side to be hung on a wall, that holds lights.
Shade A screen that prevents a light source from being viewed directly. Shades generally use opaque or
Soft Light A light source that creates gradual shadows, without a noticeable edge between lighted and dark
areas. Soft light is generally created with diffuse lighting sources, such as:
- The sun, when covered with clouds that diffuse its light.
- Lighting fixtures with lens or diffusers.
Spotlight Lighting fixture that produces a narrow downward beam, generally used for accent lighting or
task lighting applications.
SSL Acronym for solid state lighting, any type of lighting that uses LEDs to produce light, instead
of incandescent filaments, ignited gas or plasma. SSL includes OLEDs.
Step Dimming Dimming method that uses incremental and fixed lighting levels, as opposed to gradual dimming
from to OFF to 100% output.
Table Lamp A small electrical light that is used on the table. Typically provides ambient and diffuse
Task Lighting 1) Illumination designed for a work surface to provide good light, free of shadows and glare.
2) Supplemental lighting provided to assist in performing a localized task, e.g. a table lamp for
reading or an inspection lamp for fabric inspection.
Toe Kick Lighting Toe kick lighting is a great way to define the baseline edges of cabinets. It can also serve as
great night light, preventing accidents and adding intrigue to a room. Properly positioned, toe kick
lighting gives the visual illusion of floating cabinetry and can add depth to interesting floor
covering. In dimly lit spaces, the subtle light will define the room’s architecture while providing
Torchiere A floor lamp that uses a reflector on top a pole to direct its entire output upward, which is
reflected from the ceiling and walls.
Track Lighting Lighting for a room or other area in which individual spotlight fixtures are attached along a
narrow, wall or ceiling-mounted metal track through which current is conducted, permitting flexible
positioning of the lights.
Translucent Material A material that allows a partial transmission of light, generally diffusing it and eliminating
glare. Frosted glass is an example of a translucent material.
Transparent Material A material that allows most or all of the light incident on it to pass through. Clear glass is a
Troffer A recessed lighting fixture, designed to be installed in an opening in the ceiling. Troffers
typically have predetermined dimensions, such as 2’x2’ or 2’x4’.
UGR UGR stands for Unified Glare Rating. It is a metric primarily used in architectural lighting to ensure that lights selected for use in a particular space will be conducive to the maintenance of good eye health for occupants of that space through reduction or elimination of glare.
UL Label A label placed by Underwriters Laboratories, which means a product has been tested for fire
safety and electrical safety.
Uplighting Lighting method where an object or surface is lit from below, with a luminaire that directs its
output upward. The applications of uplighting are generally decorative.
Valance Lighting Lighting that is installed above the upper edge of windows, where an opaque panel blocks direct
vision of the fixture and the light is directed upward and downward as a result.
Vanity Light Lighting located above, below or to the sides of a bathroom mirror.
Voltage (V) Often considered to be the force of electrons moving from one point to another. Technically not
a force at all, but the potential for electrons to move from one point to another, as measured in
volts. Also known as the difference in electric potential between two points of different electrical
Volts (V) 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.
Volumetric Troffer A troffer that is specially designed for maximum optical performance, with a uniform lighting
distribution that eliminates both glare and the cave effect.
Wall Bracket A sturdy metal arm that attaches to a wall and provides a means for attaching a luminaire.
Wall Grazing Lighting effect where a wall with an irregular surface is illuminated so that there are both
highlighted and shaded areas. This effect is only possible on walls with granular surfaces, such as
those built from stone or exposed brick. The opposite effect is wall washing.
Wall Washing Lighting effect where a wall is illuminated so that surface irregularities are minimized, it
smoother. The opposite effect is wall grazing.
Wall-Mounted Something that’s affixed to the wall.
Wallpack Fully-encased luminaire that is designed to be mounted on an outdoor wall to provide area
Wallpacks are available in HID, CFL and LED versions.
Wash / Wash Light 1) An even, overall illumination over a large area.
2) To create such an illumination.
Watts A measurement of power or the rate at which electrons move along a wire.
Xenon An inert gas used as a component in certain lamps to produce a cooler colour temperature than
standard incandescent. It is often used in applications where halogen may normally be specified
because of a longer lamp life and lower pressure.
Yoke A sturdy, U-shaped metal bracket that attaches to opposite sides of a luminaire, such that it
allows it to tilt freely. A locking mechanism is provided to prevent slippage when the desired
position has been achieved. Also provided at the center of the yoke is a hole, stud, or receiver for
mounting the yoke.
Zenith An imaginary point directly above a particular location, typically directly above the luminaire
(at an 180° angle).
Zone Lighting In dimming, lights that are operated together. May also be referred to as Channel Lighting.
Zoom Focus A term used to describe an optical system whereby the lenses in a luminaire adjust such that a
beam pattern with a hard edge can be attained at various sizes at various distances without
sacrificing beam lumens.