Simple Lighting Glossary

Don’t know your Candela from your Kelvins? Confused between lamps, lumens and luminaires?

Not to worry, is here to wade through all the jargon in the lighting world and make your buying experience easier with our Simple Lighting Glossary.

Below are some of the most-used words and phrases in lighting terminology that we believe you’ll need to know when searching for your next spotlight, outdoor light or traditional household bulb.

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A-Z Lighting Glossary


Accent Lighting Directional lighting to emphasise a particular object, location or specific area. Examples of accent lighting are recessed lighting and track lighting.


Alternating Current (AC) – The flow of electricity which travels in waves and pulses on and off in cycle many times per second. The number of cycles per second is referred to as frequency.


Beam Angle – Measures the angular cone of light from the centre of the beam to the angle where light intensity is 50% of the maximum. The beam angle is important when selecting spotlights such as GU10’S or MR16’s.



Candela – Unit of luminous intensity (defined below) from a light source in a specified direction.


Candlepower – Old terminology for luminous intensity.


Colour Rendering Index (CRI) – The ability of light sources to represent colours. The CRI quality is based on 8 test colours against a light source in relation to a standard reference (usually a natural source of light).

A light’s CRI is the average value of the 8 colours, see below for how different light sources measure for representing colour. (table)



Colour Temperature – The colour temperature of lamp is related to the radiation of a black body of steel through a heating process. The different status of heating level is how colour temperature is determined.

Colour temperature is measured in Kelvin (K) and is scaled from 2,000k – 10,000k.



Driver An electrical device that regulates power to an LED or strings of LED’s. It works by responding to the changing needs of LED’s by providing a constant quantity of power as its electrical properties change with temperature.



Efficiency Ratio of lumen output of luminaire to that of the bare lamp.


Fluorescent A linear light source that consists of a tube filled with gas. When an electrical current is applied, the resulting arc emits ultraviolet light that excites phosphorus inside the lamp wall. This cause them to radiate a visible light.


Halogen – The gas used in Tungsten-Halogen lamps which enhances lamp life and lumen output.


Intensity – The luminous flux per unit solid angle in a particular direction. This may be expressed in either candela or lumens per steradian.


IP (Ingress Protection) The IEC (International Electro technical Commission) uses IP to define environmental protection of an enclosure against dust and moisture.

An IP rating is represented as a two digit number. The first digit defines the level of protection against solid objects, while the second digit is the level of protection against moisture. The higher the digit, the greater the amount of protection.



Kelvin (K) A measurement of colour temperature, ranges from 2,000  -10,000K.


LED A Light Emitting Diode which acts as a semiconductor light source. LED’s offer long life and high efficiency.


Lamp The actual source of light in a fixture. Fluorescent lamps can be called ‘tubes’ and some incandescent lamps ‘light bulbs’.


Lumen (LM) The measurement of light output of a lamp. Lumen is now widely used instead of watts as an indicator of lumen brightness.

Wattage cannot accurately describe brightness, especially since the emergence of energy efficient technology such as CFL and LED bulbs.


Luminaire A complete lighting unit consisting of lamp(s). It can be a part designed to distribute lighting in housing, or a necessary component such as ballast, socket etc.


Luminous Intensity –  The quantity of visible light that is emitted in unit time per unit solid angle.


PAR Lamp Parabolic Aluminised Reflector lamp. An incandescent or low voltage lamp used to redirect light from filament in a manner resembling parabolic reflector.



Reflector The part of a light fixture that shrouds the lamps and directs the light emitted from the lamp.

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Track Lighting Luminaires attached to a linear track system used in accent lighting/general applications. Track lighting can either be recessed or suspended.




Tungsten Halogen A tungsten filament lamp filled with halogen gas, in the shape of a lamp envelope made of quartz to withstand the high temperature.

A certain proportion of halogens – iodine, chlorine, bromine and fluorine – slow down tungsten evaporation, commonly enclosed in a ‘quartz lamp’.


Voltage (V) The potential difference between two points of an electrical current.


Wattage (W) The unit for measuring electrical power, as wattage is the energy consumed by an electrical device when in operation.

Wattage is calculated with Volts x Amps = Wattage. The energy cost of an electrical device = Watts consumed x hours of use.

Despite being used as a good indicator of the brightness of a product for a long time, the introduction of LED’s has resulted in products now displaying wattage equivalent to lumens.




You’ve Seen The Light…

So there you have it! The whole world of lighting terms all on one page for you to look back on whenever you’re unsure.

We appreciate however that not everyone is an expert in illumination, so if you have any further questions make sure to check out our ‘Easy guide to Colour Rendering Index (CRI)’ and ‘Emergency lighting Regulations – All You Need To Know’.