A Glossary of All Lighting Terminology Explained

A Glossary of All Lighting Terminology Explained

Lighting terminology can be quite complex. Without any prior experience or knowledge, you will find lighting to be a very tricky business. To make things a little bit easier, we have compiled a glossary of all the major lighting terms you might encounter when researching light and lighting fixtures for your home.

Accent Lighting

It focuses light on a specific object or area. It is commonly used to create visual interest in galleries and visual displays.

Aluminium Reflector

A highly reflective surface of aluminium used in most spot and flood lamps. It helps reflect and evenly distribute both the light and heat from the bulbs.

Ambient Temperature

It is the air temperature surrounding a lighting fixture. The majority of LED light bulbs have incorporated heat sinks that help them dissipate heat and perform perfectly even under extreme temperatures.


It is the measure of electrical current flowing through a circuit. Ampere, also referred to as ‘amps,’ is used to determine a bulb’s wattage.


It is a distinct type of electrical reactance or resistor fixed along the circuits supplying power to a light bulb. Its main role is to help the supplied current during various operating stages of fluorescent lamps.

Bayonet Cap

Also referred to as B22d or BC cap, it is one of the most common light bulb caps in the UK. It has two short horizontal spikes sticking out from the base. It is fitted by pushing and twisting.

Beam Angle

It is the measure of how light is distributed from the bulb. A small beam angle means the beam of light emitted is narrow and very focused, while a larger beam angle covers a wider area.

Black Light Blue

It is also referred to as UV-A light. This type of bulb emits invisible ultraviolet light hence the name UV-A light.


It is the common term used for the electric lamp in which lamps are often surrounded.

Burning Position

The position in which a lamp is designed to be installed and operated for maximum performance and safety. It can be defined by the following code letters.

  • H = vertical (base upwards)
  • S = vertical (base downwards)
  • P = horizontal


Candela is the standard measure of luminous intensity in a given direction of a source that emits monochromatic radiation of frequency 540 × 1012 hertz and has a radiant intensity in that direction of ¹/₆₈₃ watt per unit solid angle. It is abbreviated as cd.


A popular light bulb shape mainly used in decorative fittings. It is essentially a lightbulb with the shape of a candle flame, hence the name.


An element that provides electrical contact to conduct electricity to the bulb. It helps with securing the light bulb into its fitting. Some of the common caps for incandescent lamps include the ‘Bayonet’ fitting, the Edison screw, and the ubiquitous 22mm.

Ceiling Light

A lighting fixture designed to be hung from the ceiling and vertically project a beam of light onto a cloud base.

Chrome Cap

Also referred to as ‘crown silver’ lamps. They are lamps with an exceptionally high reflective coating on the front glass. The reflective coating reflects heat back into the luminaire and should therefore only be used with luminaires designed to accept them.

Colour Rendering Index

Colour rendering index (CRI) is a measure of the ability of a light source to reveal the colours of the environment around it accurately. It has a maximum score of 100, where any value above 90 is considered excellent. Any score below 80 is generally considered poor.

Colour Temperature

Different bulbs emit different colour temperatures. It is the measure of how warm or cold the light produced is. Colour temperature is represented in Kelvins (K) and measured on a numbered scale. The three basic choices of light regarding colour temperature are:

  • Warm White – bulbs with a colour temperature of less than 3500K.
  • Cool White – bulbs with a colour temperature of between 3500K and 5000K.
  • Daylight – bulbs with a colour temperature above 5000K.

Compact Fluorescent Lamp

Also known as ‘ow energy light bulbs, they use a similar technology to that of fluorescent tubes but with the types folded into a more dense design. The main advantages of compact fluorescent lamps are:

  • 80% lower power consumption than equivalent incandescent lamps.
  • 3 to 15 times longer operating life than conventional incandescent lamps.
  • Ideal for use in enclosed settings and close to delicate lampshades due to their low heat output.

The following are the two distinct categories of compact fluorescent lamps:

  • Integrated – the lamp consists of both the fluorescent tube and the required control gear all in one package. These lamps are great for the direct replacement of conventional incandescent lamps. They are often manufactured with standard BC or ES fittings.
  • Non-integrated – the control equipment is part of the fitting while the lamp is simply the folded tube. Sometime back, these were mostly used in commercial and industrial fittings but are currently being used in homes and exterior lighting.

Delivered Light

It is the measure of useful light a light source can deliver to a given area. Delivered light is measured in lux.


A dichroic light bulb that has a reflector with a special multi-layer coating on the reflector that emits light from the back of the lamp. It reflects visible light forward while transmitting heat backward through the rear of the lamp.


A device or material that diffuses or scatters light in some manner hence softening it.


The ability to fix a compatible dimmer switch onto a light bulb and use it to vary the light output.

Dimmer Switch

It is a device connected to a light fixture and used to adjust the brightness of a light bulb. When you change the voltage waveform apple to a lamp, it is possible to lower and increase the intensity of the light output.

Edison Screw

A standard lightbulb socket for electric bulbs that screws into matching threaded sockets. The Edison screw is commonly used for commercial and industrial purposes. It was developed by Thomas Edison in 1881.

Emergency Lighting

It is lighting meant for emergencies when the main power supply suffers an outage. The majority of LED light fittings contain battery-operated emergency drivers, which automatically come to life when the mains power is cut.

Equivalent Wattage

Equivalent wattages are used to compare trade-off bulbs. For example, a 100W incandescent bulb that outputs the same amount of light as a 6W LED light bulb.

Festoon Lighting

Festoon lighting comprises a cable to which big bulbs and bulbs of character are fixed at regular intervals.


It is the conducting wire or thread with a high melting point that glows in an incandescent lamp when an electrical current is passed through it. Initially, it was made of carbon. But the majority of incandescent lamps now use tungsten filaments.

Fluorescent Lamps

A type of electric lamp containing a coating of fluorescent material on the inner surface and mercury vapour whose continuous pelting by electrons from the cathode provides UV light which causes the material to emit visible light.


General Lighting Service is the typical pear-shaped light bulbs you are likely to find in almost every home.

Heat Sink

It is an electrical component incorporated into most LED bulbs and fittings. Its main purpose is to reduce the temperature by drawing heat away from the delicate components of a bulb hence a longer life span.

High-Intensity Discharge

High-intensity discharge (HID) lamps are typically used to illuminate light over large areas such as warehouses and car parks.

International Electrotechnical Commission (IEC)

An organisation responsible for the preparation and publishing of international Standards for all electrical and electronic-related technologies.


An incandescent bulb, incandescent lamp, or incandescent light globe is an electric light with an enclosed wire filament that is heated until it glows. The bulb contains a vacuum or inert gas to prevent the filament from burning.

Ingress Protection

Ingress Protection (IP) rating defines the levels of sealing effectiveness of light bulbs against intrusion from water and other foreign bodies such as dust. IP ratings consist of two numbers, with the first one specifying how protected an object is from the intrusion of solid objects and the second one specifies how protected it is from water.


The unit used to measure the colour temperature from a light source.


Any of the various devices for producing light or/and sometimes heat. Types of lamps include tubes, bulbs, capsules, and spots.

Leading Edge Dimmer

It is a popular type of dimmer switch which is surprisingly incompatible with most LED light bulbs. A leading-edge dimmer can control lower wattage loads.


It is a light-emitting diode (LED) that glows when a voltage is applied. LED light bulbs have a long life span and the ability to save on energy consumption efficiently. However, they are more expensive than fluorescent and incandescent lamps.

Long Life

The majority of light bulbs are manufactured in a “long-life” version. It means they are made of better quality components, distinct construction techniques, and more precise quality control. This term solely relies on the quality of a bulb.


The measure of the total amount of visible light emitted by a source. Lumens are denoted in lm. A higher lumen rating means a brighter lamp. Most typical light bulbs used throughout the house emit anything between 300-1000 lumens. High-powered flood lights used to light up large outdoor areas can emit an excess of up to 20,000 lumens.


The complete lighting unit consists of a lamp holder and all the other parts designed to distribute light, such as shades, reflectors, or diffusers, along with safety features.

Luminous Efficacy

It is a comparison of light output (lumens) with power input (watts) to determine the efficiency of a light source.

Metal Halide Lamps

A type of lamp that emits light by an electric arc through a gaseous mixture of vaporised mercury and metal halides. It is usually used in showroom, retail, and factory settings to create a crisp white light.

Multifaceted Reflector

It is a reflector housing format for halogens, some LEDs, and fluorescent lamps. These types of light bulbs often have a narrow beam angle hence produce a bright, focused light.

Passive Infrared Detection

A type of motion-detecting sensor used in floodlights and commercial light fittings detects a significant change in surroundings, e.g. when a person walks by.


A pendant is a light fixture that is most commonly suspended from a ceiling.

Phosphor Conversion

The process of converting one wavelength of blue light to several wavelengths that our eyes interpret as white light. It is one of the most efficient methods used to generate white LED light.


A device used to detect and regulate the light output from a particular source. A photocell sensor is regarded as a transducer that is used to detect light intensity.

Rated Life

The lifespan of a light bulb before it stops operating. Incandescent light bulbs have a filament that burns out at a high rate. LED bulbs last longer, but they gradually get dimmer with time.


A term used to describe new light fittings and bulbs that are compatible with older light fixtures. Most LED bulbs are retrofit, making it easy to replace them.


It stands for “Red Green Blue,” the three hues of light that can be combined to create different colours.

Tungsten Halogen

An incandescent lamp that consists of a tungsten filament and a mixture of halogen type of gases, including bromine, chlorine, and iodine. The benefits of tungsten halogen lamps include:

  • Slightly higher colour temperature than ordinary tungsten incandescent lamps hence emitting a bright, white light ideal for shop display lighting.
  • Smaller in physical size when compared to equivalent tungsten incandescent lamps.
  • They typically last 2000 to 5000 hours more than tungsten incandescent lamps.

Their only disadvantage is that the quartz envelope is more sensitive to contamination than regular glass light bulbs. The quartz capsule should not be touched with bare hands to avoid overheating and reducing its life span.


The standard unit for measurement of power. The wattage of a bulb is the amount of power it consumes to emit light. Since some lamps are more or less efficient in converting electric power to light, the Watt is not used to measure brightness.

28th Apr 2021

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