GLOSSARY

GLOSSARY

We invite you to explore the glossary below, featuring clear and accessible definitions of commonly used terms in lighting, design, and architecture. The explanations provided reflect the widely accepted meanings within the lighting design community, including key terms, acronyms, and industry-specific language.

A

AC

Acronym for alternating current, which describes a source where the voltage changes polarity multiple times per second, with a frequency of 50 Hz or 60 Hz depending on the country.

ACCENT LIGHTING

Lighting that focuses its output in a narrow beam, drawing attention to specific decorative features or objects, making them stand out from their surroundings. Accent lighting is also useful in retail applications, where it can be used to draw attention to specific products and make them seem more appealing.

AMBIENT LIGHTING

General lighting used to provide visibility in a built environment. Ambient lighting includes both artificial and natural lighting, and does not include task lighting and accent lighting.

B

BACKLIGHT

The lighting output of outdoor fixtures that is emitted opposite to the intended direction, generally an undesirable effect. For example, if the pole lamps in a parking lot emit backlight towards adjacent 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 around its edges. Backlighting is a type of accent lighting, and is commonly used to draw attention to works of art.

Backlighting should not to be confused with backlight, an undesirable lighting effect that can be produced by outdoor fixtures.

BASE

The part of a lamp that connects to the lighting fixture, providing both physical support and electric power for the lamp. A lamp and fixture can only be used together if the lamp base matches the fixture socket. The bases of most residential lamps use either a screw or multiple pins.

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

 

BEAM ANGLE

Also known as beam spread, the beam angle is a value that describes the downward light cone emitted by a lighting fixture with a reflector. The beam angle is measured between the downward direction, where the lamp provides maximum lighting intensity, and the direction in which intensity drops to 50%. In other words, a lamp with a large beam angle spread its lighting into a wider cone.

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BOLLARD

A type of lighting fixture commonly used outdoors, consisting of a short and broad post with a lamp on top. Bollards generally accomplish a double function, providing both outdoor lighting and decoration.

BULB

A transparent casing that contains a light source, generally made from glass.

C

CANDELA (CD)

Measurement unit for luminous intensity, which is the amount of light emitted in a particular direction. Not to be confused with the lumen (lm), measurement unit for the total lighting output of a lamp or fixture, without describing a particular direction.

CANOPY

Part of a lighting fixture that covers the outlet box and wiring connections. Canopies often have decorative features.

CHANDELIER

Derived from "chandler" (candle maker), a chandelier is a designer/decorative light that hangs from the ceiling and consists of several branch-like parts that host lights or candles.

COLOR RENDERING INDEX (CRI)

A metric used to describe how faithfully a light source can render the true colors of objects and spaces, where natural light sources like the sun have a perfect index of 100. Using lamps with a high CRI value is very important in high-end interior design, as they enhance the visibility of décor and fine details.

CONTINUOUS DIMMING

Dimming method where the lamp output can be adjusted at any level between OFF and 100% output, without incremental steps. See Dimmer.

COOL WHITE

A light source with a correlated color temperature of around 4100K. The term comes from the fact that light sources at this color temperature value do not have the characteristic yellow hue of incandescent bulbs or warm white LED lamps.

CORRELATED COLOR TEMPERATURE (CCT)

Unlike the CRI, which describes how faithfully a light source represents other objects, the correlated color temperature (CCT) describes the color output of the lamp itself. Some common CCT values include:

 

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 concentration.

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 only color temperature. It is also important to note that the CCT is not the real operating temperature of a lamp - it is the temperature to which you would have to heat a black body to make it glow with the same color. For example, an LED bulb with a CCT of 5000K glows in the same color as a black body heated to a real 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 fixtures are hidden in ledges. Cove lighting is often used for decorative purposes because it can emphasize the borders of walls, as well as ceiling features.

D

DALI

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

DC

Acronym for Direct Current. Used to describe a power supply where the flow of electricity always takes place in the same direction, such as that provided to LED arrays by their drivers.

DIFFUSED LIGHT

Light produced by an extended surface, either directly or through reflection. Diffused light provides a uniform and soft distribution that minimizes shadows.

DIFFUSER

A piece of glass or acrylic that has the purpose of scattering the light from a bulb, which results makes lighting more uniform and eliminates glare.

DIMMABLE

Adjective used to describe a lamp or fixture whose lighting output can be modulated with a dimmer. See Dimmer.

DIMMER

A device that regulates the lighting output of a lamp by controlling the power supplied. Dimmers can be used to make indoor environments more customizable and personal, and are also useful to save energy. It is important to note that not all lamps are compatible with dimmers, and incompatible types may be damaged.

DIRECT LIGHTING

Lighting where more than 90% of the light goes directly from the source to the area you wish to illuminate.

DIRECTED LIGHT

Light produced by point surfaces, which results in a concentrated output that accentuates edges and shadows. Directed light normally causes glare when the sources is viewed directly.

DOWNLIGHT

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

DRIVER

Piece of electronic equipment that transforms the main supply voltage into a lower DC voltage that is appropriate for LED lighting. Some LED lamps have a built-in driver, while others require one to be connected externally, just like the ballasts used by fluorescent and HID lamps.

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E

EDGE LIT LED

A type of LED fixture that uses a transparent acrylic pattern with etched dots, lines, or patterns. The panel is encircled by an array of LEDs, and the etched pattern refracts the light uniformly in all directions.

EFFICACY

Describes how effectively a lighting fixture can convert electric power into lighting, measured in lumens 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

The conversion ratio between lighting power output and electric power input, measuring both quantities in watts. Not to be confused with efficacy, which describes the ratio between lumen output and watts consumed. Since lumens describe lighting output better than watts, efficacy tends to be a much more useful concept in lighting design.

 

EMERGENCY LIGHTING

Lighting designed to provide visibility when the normal lighting system fails, for example during blackouts. Emergency lighting is equipped with batteries, allowing it to operate long enough for a building to be evacuated.

F

FILAMENT

The wire coil that is heated to produce lighting in incandescent and halogen lamps, normally made from tungsten.

FLICKER

A phenomenon where a lamp blinks repeatedly, often caused by power supply issues, or a faulty ballast or driver.

FLOODLIGHT

High-power lighting fixtures that typically use HID bulbs or their LED equivalents. They are generally used outdoors to emphasize specific objects or areas.

FLUSH MOUNT LIGHTING / FLUSH MOUNT LED LIGHTS

This kind of lighting is mounted to the ceiling with little or no gap between the ceiling and the light.

FOOT-CANDLE (FC)

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

FROSTED LENS

A white lens that is translucent but not transparent, which diffuses the output of a lamp.

G

GLARE

Visual impairment caused by a bright source of light, directly visible or reflected by a surface. There are two types of glare:

Discomfort glare causes an instinctive reaction to close the eyes and look away. This is the type of 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 a light source gets reflected on your laptop screen, for example, it does not bother your eyes but distinguishing objects on the screen may be impossible.

H

HEAT SINK

A lamp or luminaire component that is used to dissipate heat effectively. Heat sinks normally use materials with high thermal conductivity and have a fin-like geometry so that their surface area in contact with the air is maximized.

HIGH-BAY LIGHTING

Lighting systems designed for ceiling heights of 25’ or more, commonly found in sports complexes, warehouses, or industrial locations. See low-bay lighting.

I

ILLUMINANCE

The luminous flux on a surface, per unit of area. The illuminance requirements of built environments 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.

ILLUMINATION

The use of lighting for practical or artistic purposes.

INDIRECT LIGHTING

Lighting technique based on reflecting the output of a lamp on surfaces. An example is the lighting provided by torchiere fixtures, which emit their beam towards the ceiling to be reflected back down.

INTEGRATED LIGHTING FIXTURE

A type of lighting fixture that offers superior energy efficiency, by using a specially-designed LED array and internal geometry. Integrated lighting fixtures are generally more efficient than lamp-based LED fixtures, but they make retrofits more expensive because the entire fixture must be replaced, not only the lamps and ballasts.

INGRESS PROTECTION (IP) RATING

Ingress Protection rating, a two-digit code that indicates the resistance of a lighting fixture to solid particles and liquids, where higher digits indicate enhanced protection. The first digit indicates protection 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.

K

KELVIN (K)

Measurement unit for temperature, although in the lighting industry it is more commonly used to indicate the correlated color temperature (CCT) of light sources.

L

LAMP

The specific component of a lighting fixture that emits light. They generally come with standard bases that fit into the sockets found in compatible fixtures. Some lamps have built-in ballasts or drivers, while others are connected to an external one contained in the fixture.

LAMP LUMEN DEPRECIATION (LLD)

A progressive reduction in the luminous output of a lamp throughout it service life.

LAMPHOLDER

The part of a lighting fixture that provides support and power for a lamp with a matching base.

LED

Acronym for light-emitting diode, a solid-state component that emits light when exposed to electric current. LED lighting represents the state-of-the-art in the industry, outclassing most other types of lighting in terms of energy efficiency, design flexibility, and colors of light available.

LEED

Leadership in Energy and Environmental Design, a resource efficiency certification framework for buildings, developed by the US Green Building Council.

LENS

Lamp or luminaire component that has the goal of dispersing the lighting output so that the desired distribution pattern is achieved.

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LIGHT LOSS FACTOR (LLF)

A factor used in lighting design to account of the degradation in luminous output over time. The LLF 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 designed to provide 50,000 initial lumens (50,000 lm x 0.80 = 40,000 lm).

LIGHT TRANSFORMER

Also referred to as dimmer switches, light transformers are electrical devices that are used to change the voltage of a circuit to make the light dimmer or brighter.

LINEAR LIGHTING

Multiple LEDs (light-emitting diodes) aligned in a single strip and used for creating uninterrupted lines of directional lighting.

LM-79

IESNA standard that establishes the procedure to test the photometric and electrical properties of LED lighting.

LM-80

IESNA standard that establishes the procedure to test the lifespan of LED lighting.

LOUVER

A translucent or opaque screen that blocks direct visibility of a light source and eliminates glare.

LOW-BAY LIGHTING

Lighting systems designed for ceiling heights below 25’. See high-bay lighting.

LUMEN

Measurement unit for the lighting output of lamps or fixtures. The total lumens emitted and their spatial distribution are of paramount importance when creating appealing and luxurious indoor spaces. In lighting, lumens can be compared to miles traveled and watts can be compared to fuel consumption.

LUMEN MAINTENANCE LIFE

A metric used to describe the time in which the output of a lighting product diminishes to a specific percentage of its initial value. The lumen maintenance life is measured in hours and displayed by the letter L plus two digits. For example, the following lumen maintenance life would describe a product whose output decreases to 70% after 60,000 hours of use: L70 = 60,000 hours

 

                                                                                                                                                       

LUMENS PER WATT

Lumens Per Watt (LPW) is the light output per unit of energy consumption and it reflects the lighting system's efficacy.

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).

LUMINAIRE

A complete and functional lighting fixture. A luminaire includes the lamp, the ballast or driver, internal wiring, reflectors, lens and any additional components required to deliver light.

LUMINAIRE DIRT DEPRECIATION (LDD)

Progressive reduction in the output of a luminaire due to dust accumulation.

LUMINAIRE EFFICIENCY

The ratio between the lumens emitted by a complete luminaire to those emitted by the lamps within. A portion of lighting is always lost due to internal geometric features and reflection. Not to be confused with luminous efficacy.

LUMINANCE

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

LUMINOUS FLUX

Total output emitted by a light source, measured in lumens. The luminous flux describes the total lighting output of a lighting fixture without considering direction. Not to be confused with luminous intensity.

LUMINOUS INTENSITY

Lighting emission in a specific direction, measured in candelas. Luminous intensity changes depending on the viewing angle. Not to be confused with luminous flux.

LUX

Measurement unit for illuminance, or lumens per unit of area. One lux is equivalent to one lumen per square meter. A key component of lighting designed is achieving a suitable illuminance level depending on the application at hand.

M

MOUNTING HEIGHT

MR LAMP

MR is an acronym for multifaceted reflector, a component used to shape the output of a light bulb 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.

N

NEMA ENCLOSURE TYPE

A numeric code that describes the degree of protection offered by an enclosure, according to the NEMA 250-214 standard. For example:

O

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

Acronym for organic light-emitting diodes, flexible polymers based on organic carbon molecules, where the light source is spread across a surface as opposed to a point source.

OPAL GLASS

Semi-translucent white glass that owes its milky finish to the ingredients added to clear glass. It is used for diffusing light.

 

P

PENDANT LIGHT / PENDANT FIXTURE / PENDANT LAMP

A lighting fixture that is designed to hang from the ceiling, and which often uses a shade to prevent glare. Pendant lights can be used for both general and task lighting.

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.

R

RECESSED LIGHTING / RECESSED FIXTURE / RECESSED LUMINAIRE

Also known as pot light, canister light or downlight, recessed lighting fixtures or luminaires are installed into the openings in a ceiling, appearing as if the light is shining from an elevated hole.

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.

RETROFIT

A lighting system upgrade, generally with the goal of improving energy efficiency and site safety.

ROOM UTILIZATION FACTOR

Ratio between the light that reaches the work plane and that emitted by the luminaires in the room.

S

SHADE

A screen that prevents a light source from being viewed directly. Shades generally use opaque or translucent materials.

Shadow Casting Light Fixtures

Lamps that are designed to cast light and shadows, creating intricate geometrical or abstract patterns on surrounding surfaces.

SPOTLIGHT

Lighting fixture that produces a narrow downward beam, generally used for accent lighting or task lighting applications.

STRIP LIGHT

Flexible, dynamic and customizable, strip lights can be cut and stuck anywhere, according to project requirements.

SUSPENSION LIGHT / SUSPENSION FIXTURE / SUSPENSION LAMP

See Pendant Light / Pendant Fixture / Pendant Lamp

 

T

TASK LIGHTING

Lighting fixtures with the goal to improve visibility in an area where specific tasks will be carried out, hence their name. The use of under cabinet lights for food preparation areas in kitchens is an example of task lighting.

TRACK LIGHTING

Lighting configuration where several fixtures are mounted on a common track, which provides them with power and allows each of them to be oriented in a different direction.

TROFFER

A recessed lighting fixture, designed to be installed in an opening in the ceiling. Trofferstypically have predetermined dimensions, such as 2’x2’ or 2’x4’.

U

UNDER CABINET LIGHTING

Installed under a cabinet or shelf, this lighting is used to produce localized lighting and can also serve as a night light. It can come in LED, fluorescent, incandescent versions.

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.

V

VOLTAGE

The electric potential difference between two contacts. Voltage drives electric current through lighting fixtures and other appliances, just like pressure drives the flow of water in plumbing installations.

W

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 seem smoother. The opposite effect is wall grazing.

WARM WHITE

White light that is characterized by a yellow tinge. The term is generally used for lighting with a correlated color temperature (CCT) of around 3000K.

WATT

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

WATTS TO LUMENS

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

WORK PLANE

The horizontal plane where activities are carried out, typically 30 inches above the floor. Lighting designs are generally based on providing a specified illumination level at the work plane.