The Encyclopedia of Lighting


Many questions can arise when it comes to lighting, and sometimes the answers can be a little difficult to understand. We aim to clear things up with our lighting encyclopedia, shedding light on lighting terminology.

A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z



AC stands for “Alternating Current”. It is an electric current that changes polarity periodically. It may be increased or decreased by a transformer and is the form used in businesses and residences.

Accent Lighting

Accent lighting is a form of lighting used to highlight features, ornaments and or structures.

Ambient Lighting

Ambient lighting is also known as “general lighting” and is the primary lighting source of a room.


An amp (ampere) is a base unit of electrical current. It is a measure of current.

Art Deco

Art Deco was a movement in the 1920’s – 1930’s which focused on signature geometric motifs. Clean and bold lines creating a modern appeal.

See more about Art Deco here: Lighting 100 Years of Art Deco

Art Nouveau

The Art Nouveau style shares similarity with the Arts and Crafts movement. Designs crafted by Charles Rennie Mackintosh and Louis Comfort Tiffany which feature floral patterns are iconic of this style. Sometimes referred to as the “Glasgow Style” in the UK.

See more about Art Nouveau here: Tiffany Lighting, Art Nouveau

Artisan Lighting

An artisan is a crafts person specialising in a specific trade to make partially or entirely hand mate products. Artisan lighting refers to lighting that is hand crafted or finished.

See more about Artisan Lighting here: Lighting Trend Artisan Lighting



When something is back lit it means there is a light source projecting light back onto the surface in which it is mounted. If a light fitting is back-lit it will have a highlighting effect on the wall or ceiling it is mounted on.


A baffle refers to part of, or an accessory of, a lamp shade which hides the light source from direct view whilst still allowing light to escape.

Bare Bulb Lighting

This is a popular and ever growing trend in lighting. It puts bulbs and light sources in the foreground utilising see through shades – or none at all.

See more about Bare Bulb Lighting here: Lighting Trend Bare Bulb Lighting

Bathroom Lighting

Bathroom lighting is specially made to have protection from water and steam. This is measured by Ingress Protection ratings. A minimum of IP44 is required for bathroom use.

See more about bathroom lighting here: Definitive Guide To Bathroom Lighting


A batten light is usually referred to as a tubular architectural style light fitting. Normally one or two fluorescent or LED tubular bulbs. A good choice of functional lighting for places such as car parks and garages.

Bauhaus Lighting

This is a lighting trend which features light fittings inspired by the designs of the Staatliches Bauhaus, a German art school. Geometric shapes, primary colours and linear motifs are the forefront of this design.

See more about Bauhaus lighting here: Bauhaus Lighting

Bayonet Cap

Bayonet cap refers to a type of light bulb fitting. The Bayonet comes in two types, an SBC (small bayonet cap – or B15) and a BC (bayonet cap – or B22).

Bluetooth Lighting

Bluetooth is a wireless connection between devices. There are light fittings available which use this technology in order to be operated and or (providing one is built in) play music through a speaker.

See more about Bluetooth lighting here: Technical Lighting

Boho Lighting

Lighting with a Bohemian influence. This style is arty, expressive, bright and creative. Think wicker and tie dye with a sense of brave styling.

See more about Boho lighting here: Lighting the path to Boho


Candela (cd)

A Candela is a unit of luminous intensity. A common candle emits 1 candela.


In lighting a candelabra refers to the style of a light fitting, representative of a multi arm candle stick or candle tree.


A cap refers to the fitting type of a light bulb or the socket on a light fitting. For example an Edison Screw or Small Bayonet Cap.

Ceiling Light / Ceiling Fitting

A ceiling light is a light fitting which is fixed to or suspended from the ceiling. This ranges from spotlights to chandeliers.


A chandelier is a decorative and often multi-arm light fitting. Coming in a variety of styles and designs these light fittings are often elaborate and perfect for adding glamour to an indoor space.

See more about chandeliers here: Definitive Guide to Chandeliers

Class 2

Class 2 means double insulated. Light fittings which are double insulated have been designed to operate safely without the need of an earth wire. They have an inner layer to ensure the electrical parts can never come into contact with the outer casing, this makes sure exposed metal can not become live.

See more about double insulated lights here: What Are Double Insulated Lights?

Colour Temperature

Colour temperature is measured in Kelvins, it is the scale used to measure how warm or cool a source of light appears. The lower end of the scale is a warmer light and the higher end of the scale is a cooler light.

See more about colour temperature here: What Does the Colour Temperature of Bulbs Mean?

Compact Fluorescent (CFL)

A compact fluorescent lamp is a fluorescent tubular light source which has been designed in a way to be used in standard light fittings. These often appear as spiral shaped tubes and come in various caps such as Edison Screw. These were designed to replace the standard incandescent (60 watt etc) bulb.

Concealed Lighting

Concealed lighting refers to lights which are hidden from view such as cabinet strip or spot lighting. Provide a functional service but are not decorative in design.

Continuous Dimming

If a light has continuous dimming functionality then the light output can be controlled smoothly from off all the way to full brightness. Not altered in predefined stages.

Cool White

Cool white is a colour temperature that refers to a particular colour of light. In this case it emits a bluer light and ranks higher on the Kelvin scale.

CRI (Colour Rendering Index)

The colour rendering index is a scale which measures how well a light source maintains the true colour of the object it is illuminating. It has a rating of 0-100 with 100 being the most efficient at maintaining the true colour.

Curated Lighting

A trend in lighting which originated from the Victorian era. It focuses on box shapes, lanterns and clear glass.

See more about Curated Lighting here: Curated Lighting Trend



Daylight in lighting refers to a specific colour temperature. In this case it’s a colour which most closely represents natural daylight. This usually appears between 5,000 and 7,000 on the Kelvin scale.


DC stands for “Direct Current”. It is a constant flow of current. Most electronics have a DC power supply.


Dichroic material can appear as two different colours depending on the light conditions around it.


In lighting a diffuser is a piece of material which softens and disperses the light emitted from a light source. For example an opal glass sheet at the bottom of a ceiling light shade.


If a light fitting or lamp is dimmable it means the output of light can be manually raised or lowered accordingly.

Direct Lighting

Direct lighting refers to lighting which is designed to project light onto a specific object or surface. Such as a spotlight with a small beam angle.

Double Insulated

Double insulated (class 2) lights are made specifically to be used without need of an earth wire. It has an added insulation within it to ensure no electric parts can touch the outer casing, preventing it from becoming live.

See more about double insulated lights here: What Are Double Insulated Lights?


Downlights are compact forms of lighting which either surface mount to, or recess into the ceiling. They provide ambient light for a room.


A driver (LED Driver) is used to regulate the power supplied to an LED or LED’s. These are often built into LED fittings or supplied with necessary LED’s. Without a driver LED’s would likely burn out.


A drum refers to the drum-like shape and style of a lampshade. E.g: A drum shade.

Dual Lit

Dual lit is a term often used in table lamps. It usually means there are two light sources, one being the general light output and the other often hidden inside the base to provide a glow from within. It can also refer to wall lights which also feature an additional reading light, usually used as a bedside light.

Dual Mount

If a light fitting is dual mount it means it can either be fitted flush to, or hanging from the ceiling (spec depending).


Easy Fit

An easy fit (non electric) refers to a lamp shade which can be installed to an existing pendant suspension with no wiring required.

Edison Screw

Edison Screw refers to a type of light bulb cap or light fitting socket. This comes in two (standard) types – Edison Screw (ES/E27) and Small Edison Screw (SES/E14).

Emergency Lighting

Emergency lighting is a form of lighting which comes with a special battery powered backup supply. This allows the light fitting to come on (or remain on) in the event of a power cut. This is usually used in hospitality settings such as hotels and restaurants.

Energy Saving / Energy Efficient

An energy saving, or energy efficient, light source is a light source which uses a minimal amount of energy to operate whilst maintaining a high output of light. Such as an LED bulb using only 6 watts but providing around 600 lumens.



Festoon lights are string lights suitable for outdoor use. They normally have multiple IP rated Edison Screw or Bayonet Cap lamp holders sited along a wire. Great for decorative lighting.


In lighting a filament refers to a wire thread inside a light bulb which is heated until it glows. This is seen most notably in traditional incandescent bulbs (the central strand which lights up).


A fitment is a fixed item. In lighting this refers to any light fitting which is fixed to a surface such as a ceiling light or wall light.

Fitting / Fixture

A fitting refers to a light which is (or is required to be) fitted to a surface to provide illumination.


A form of lighting which uses mercury gas to produce UV (ultraviolet) light. A tubular shaped bulb often used in a batten fitting.

Flush Mount / Flush Fit

A flush mount or flush fit ceiling light is a light fitting which has a minimal projection from the mounting surface. It has no hanging suspension or stem. Great for low ceiling heights.

Foot-candle (fc)

A foot-candle is a unit of illumination that is equal to one candela at a distance of one foot.



A G9 is a type of light bulb cap. It features two small hoop like clips which slot into the designed light socket. It’s usually a small compact capsule bulb available in a halogen or LED form.

General Lighting

Otherwise known as ambient lighting this is the overall main light source of a room. Generally the main ceiling light or collection of down-lights.


Ghosting is a phenomenon that occurs when an LED light source continues to glow after being switched off. This happens when there is some residual energy in the circuit being picked up.


GLS refers to the size and shape of what many consider to be a traditionally “standard” light bulb.

GB (Golf Ball)

A golf ball refers the size and shape of a small rounded light bulb. Hence the namesake.


A GU10 is a reflector bulb with two knobs at the cap which twists into a socket of the same kind. Available in halogen or LED.



A halogen bulb is an incandescent lamp made up of a tungsten filament inside a compact glass with a mix of an inert gas and a small amount of a halogen. These produce a high output of light but get extremely hot.

Hard Wired

If a light fitting is hard wired it is wired into the mains circuit and operated by a separate main switch. Such as a ceiling light for example.



Incandescent refers to the traditional standard light bulb. It is an electric light source with a wire filament which is heated to the point it glows to emit light.

Indirect Lighting

Indirect lighting is a form of lighting which projects light onto the ceiling or wall in order to reflect light into the room. It doesn’t emit light directly into the room such as a spotlight.

Integrated / Integral

In lighting the term integral often refers to the bulb or light source, this means it is built into the light fitting. This is usually the case with LED light fittings.

IP ratings / Ingress Protection Rating

An Ingress Protection Rating is a rating given to a light fitting to determine its protection against solids and liquids. IP is followed by two numbers, the first to represent protection from solids and the second to represent protection from liquids. As an example a bathroom light should be IP44 rated.

See more about IP ratings here: Definitive Guide to Bathroom Lighting


Iridescent is a finish which appears to change colour based on the angle you view it and the lighting shone upon it.


J arm

A J arm refers to the shape of a light fittings arm structure. It has a downward stem and curves up toward the end.


A joule is a unit of energy. One joule is the work needed to produce one watt for one second.



A Kelvin is a measurement of colour temperature. It refers to the Kelvin scale which determines whether a light source is on the warm or cool end of the scale. The lower the Kelvin, the warmer the light.

See more about Kelvins here: What Does the Colour Temperature of Bulbs Mean?

Kilowatt (kW)

A kilowatt is a measure of one thousand watts of power.

Kilowatt Hour (kWh)

A kilowatt hour (kWh) refers to 1000 watts being sustained for 1 hour. You are charged in kilowatt hours when it comes to electrical usage.


Lamp holder

A lamp-holder refers to the socket which houses the light bulb in a light fitting or lamp. These come in various caps including Edison Screw and Bayonet Cap.


Lamps does not only refer to portable table or floor lamps, this also (and commonly) refers to light bulbs.

Layers of Light

Layers of light refers to 3 main types of lighting. Ambient (general), task and accent.

Leading Edge Dimmer

A leading edge dimmer switch is a standard style dimmer switch. They are used to dim lamps but have a high minimum load requirement. This means if you are using LED light sources this type of dimmer switch may not be compatible.


LED stands for “Light Emitting Diode”. It is an extremely efficient source of lighting which requires a low number of watts to operate but provide a high output of lumens.

See more about LED’s here: What Are LED’s?


Levels refers to the measure of light in a room. There are recommended light levels required for certain rooms. They are measured in various ways including foot-candles, lux etc.

Lighting Control Systems

A lighting control system is a smart network which allows lighting to be operated from a central computer system or device.

Low Voltage

A low voltage light fitting has a built in or a separate (and required) transformer to lower the voltage it uses from 230v to 12v.


A lumen is a measure of light output. It determines how bright a light source is.

See more about lumens here: What Are Lumens?


A luminaries refers to a complete electric light fitting. For example a table lamp with shade and bulb.


In lighting this refers to a luminous quality, a fresh or bright colour has luminosity.

Lux (lx)

A unit of illuminance. Equal to one lumen per square metre.



A modular lighting system refers to lighting made up of components which can be customised to suit the need. This is predominantly LED.

Mother and Child

This is a popular floor lamp design which features a main light source (mother) and a separately switched smaller reading light (child).


Natural Light

Natural light refers to sunlight, natural light in a room simply refers to light which enters from outside. It can also refer to the colour temperature of a light source which closely replicates this (natural white).

Non Electric

A non electric refers to an easy fit lamp shade. It simply fits onto your existing pendant suspension without need for wiring or power.



This is usually a translucent white material (often glass) which is predominantly used as a diffuser or shade.


A white material with a slight iridescent effect.


Opaque describes a material which does not allow any visible light through. For example: Metal.

Ornamental Lighting

An ornamental piece of lighting describes a light fitting which is as much a structural ornament as it is a light. As good off as it is on.


When a material is oxidised it has chemically reacted with oxygen. In lighting this will refer to the finish of the material, it will give a somewhat weathered effect.


Pathway Lighting

This refers to lights which are suitable for illuminating outdoor pathways. Such as recessed garden spotlights, garden spike lights or downward facing wall lights.


A patina is a result of oxidation on a surface which gives an aged appearance.


A pearl finish is a white finish with a satin sheen, sometimes with a subtle iridescence.

Pelmet Lighting

This form of lighting refers to lighting using a concealed light source in an alcove. It is a form of accent lighting.

P.I.R (Passive Infra-Red)

This stands for “Passive Infra-Red”. It is a term used normally to describe a sensor which is either in built to, or can be wired to a light fitting to allow it to switch off when it senses movement. These are usually utilised outdoors.

Plug in Powered

If a light is plug in powered it simply means it has a standard plug wired to it in order to be used. It does not need to be wired into the mains.

Portable Lighting

A portable light refers to any luminaire which is not fixed to a surface. Such as a table lamp.


A prism is a transparent object with polished surfaces which refract light.

Prismatic Glass

A glass which resembles a texture made up of multiple prisms. A textured glass which refracts light.




In lighting if something has a radiance it refers to something that gives off light rays.

Reading and Task Lighting

This is a light layer used to provide light for a desk or a chair for reading. It’s lighting required to do a task.

See more about reading and task lights here: Shedding Light on Reading and Task Lamps


A rechargeable light source (often portable) is able to be used wirelessly and replenished once it has run out of power.

Remote Operated

A light which can be operated with a separate (usually supplied) remote control.


A replica is designed to replicate an original and often well known piece. Such as a replica of an original Tiffany lamp.


Similar to replica, this means to create a copy in similar likeness to the original item.

Retro Fit

In lighting retro fit refers to an updated light source designed to fit into the existing (potentially older) fitting. For example a Bayonet Cap LED light bulb can retro fit into an old bankers lamp of the same cap.


This stands for “Red Green Blue”. This is a term used for a light source which is colour changing, it is an additive colour model that can create all the colours in the spectrum.

Rise and Fall

A rise and fall light refers to a light designed to be adjusted in height as and when required. A pull up, pull down mechanism or counter weighted mechanism.



A sconce refers to a fixed wall light.

See more about wall lights here: Definitive Guide to Wall Lights

Semi Flush

A light fitting which is semi flush is fixed to the ceiling and only structurally projects a small amount. It does not hang into the room or fit completely flat to the ceiling.


A sensor often refers to a P.I.R motion sensor but can also refer to a sensor of surrounding light, such as a nightlight.

Smart Lighting

This refers to lighting which has additional technology allowing it to either be operated by remote, separate device, change colour and more. It does more than just be switched on by a mains switch.

See more about smart lighting here: Smart Lighting How To

Solar Lighting

If a light is solar powered it has an inbuilt solar panel allowing it to absorb sunlight to power it.

Speaker Lights

Lights with an in built speaker. These are usually Bluetooth operated to connect to your smart device.

See more about technical lighting here: Technical Lighting

Step Dimmer

A step dimmer system is a form of lighting which can be adjusted in brightness but only in predefined stages (usually 3 levels).


A submersible light is one which can be fitted somewhere which will be covered by water. These are low voltage and have an IP rating of at least IP67.

See more about water safe lighting here: Definitive Guide to Bathroom Lighting

Surface Mount

A light which is surface mounted it fitted onto a surface, it does not recess into a cavity.

Swing Arm

If a light fitting has a swing arm it means the arm has a hinge allowing the light source to be manoeuvred away from its mounting point.


A switch operates the light fitting. If a light has an in built switch it is considered “switched”. These come in a variety of styles including: pull cord, rocker, toggle, push bar, touch, inline dimmer and more.


Task Lighting

A layer of light consisting of light sources such as desk lamps to provide light to read by.

See more about reading and task lights here: Shedding Light on Reading and Task Lamps


Tiffany lighting refers to lights inspired by the works of Louis Comfort Tiffany, consisting of styles from the Art Nouveau and Art Deco periods.

See more about Tiffany style lighting here: Tiffany Lighting

Touch Lamp

A touch lamp is a light source operated by touch. These are usually step dimmable or continuous dimmable.


Track lighting refers to lighting that is housed along a track or bar. Sometimes modular allowing additional light sources to be added and sometimes fixed spotlights.

Trailing Edge Dimmer Switch

A trailing edge dimmer switch is a newer version of dimmer switch which negates issues such as buzzing. Most notably however they have a much lower minimum load than leading edge dimmers. This means they are more suited to dimming LED light sources.


A transformer is a device which reduces or increases the voltage of an AC current. Typically in lighting it is an inbuilt or separate device that changes the voltage of a light from 230v to 12v.


Under Cabinet

An under cabinet light is a concealed form of lighting often used in kitchens to light up a work surface. They can also refer to spotlights found inside cabinets to highlight contents.


If a light is considered “unswitched” this means it does not have an inbuilt switch, so it will require to be hard wired into the mains and operated by a separate mains switch.


Uplighting, or uplighter, is a form of indirect lighting which projects light upward onto the ceiling to reflect light into the room.


A USB (Universal Serial Bus) is a socket to provide connection and or power supply to devices. If a light source has an in built USB socket it can either provide charge for your device and or be charged itself for wireless use.

See more about lighting with USB sockets here: Technical Lighting


Vanity Lighting

This is a form of lighting used to provide illumination in front of a mirror. This could be an over mirror light, light by the side of a mirror or a self illuminated mirror.

Vaulted Ceiling

A vaulted ceiling is a ceiling which is angled or arched, typically creating a higher than average ceiling height.

See more about vaulted ceilings here: How To Light a Sloping Ceiling


Similar to patina, verdigris is the green pigment that forms on some metals through oxidation (exposure to air over time)


Voltage forces electric charges to move in a conductor or wire. A volt is the work needed to move a charge between two points. The mains voltage in the UK home is 230v, when a transformer is used it usually changes down to 12v.


Warm White

Warm white refers to the colour temperature of a particular lamp. Often recognised as the “traditional” bulb colour, warm white is lower on the Kelvin scale and has a warmer amber glow.


A washer refers to a type of wall light which “washes” part of the wall it is mounted on with light. It’s a form of indirect lighting.


A watt is a unit of power. If a light source is stated to be 6 watts then it uses 6 watts of power in order to operate.


Weathered refers to an aged or deteriorated finish.





In lighting, zones refers to bathroom zones. Each zone requires a specific IP rating in order to be deemed safe.

Zone 0 – This is inside the bath or shower itself. Lights in this zone need to be low voltage and have an IP Rating of at least IP67.

Zone 1 – This is the area above a bath or shower up to 2.25 metres from floor level. An IP rating of IP44 is required here.

Zone 2- This an area of 0.6 metres added on top of the previous zone (1). This also includes the area above any sink 0.6 metres from the taps.

Not Zoned (Previously Zone 3) – This no longer requires a specific IP rating. Any fitting can be used unless specifically stated otherwise. However with the large range of IP44+ lighting we offer we would always recommend sticking to IP44.

See more about bathroom lighting here: Definitive Guide to Bathroom Lighting

We hope our lighting encyclopedia has answered your questions. If you were unable to find the terminology you’re looking for and think it should be listed please feel free to contact us.