These explanations are provided for general information and are not intended to form comprehensive or technical definitions.

Colour rendering
The ability of artificial light to display the true colour of an object that it strikes

Colour temperature
The colour of light emitted from an artificial source

Full cutoff
Restriction of light from being directed at or above the horizontal for the installed luminaire

Illuminance
Measure of light distributed by an artificial light source

Illuminate
General expression for the provision of artificial lighting

Illumination
General reference to artificial lighting or its perceived brightness level

Lamp
Artificial light source

Lens
Flat or curved luminaire screen made of transparent or semi-opaque material

Light fitting
See 'Luminaire'

Luminaire
Electrical appliance to distribute artificial light, consisting of a lamp and optical system contained within a shield or housing

Luminance
Measure of light arriving on an object or surface

Optical system
The components of a luminaire used for light distribution, including a lens and reflector