Lamp
Component of luminaire which emits light, e.g. from a discharge or incandescent filament. Commonly known as a 'bulb' or tube'. See a comparison chart; and a discussion of startup energy requirements of fluorescent
Latent heat
Heat absorbed or released, without any change in temperature, during a change of phase to or from vapour, liquid or solid (see also sensible heat)
League table
Method of presenting lists ranked by best, worst, biggest, etc.. Needs to be used with caution when applied to energy performance because small measurement errors can precipitate wild changes in rankings of closely-grouped results. The term is sometimes used in energy management software to denote a list of users ranked merely by size, which is not very illuminating. When applied to the cost of deviations from expected consumption, however, one obtains the overspend league table which acts as a prioritised and filtered exception report.
LED
Light emitting diode; a semiconductor light source.
Lighting
Not always significant in terms of expenditure, but extremely important from a psychological standpoint. Click here for tips on saving lighting energy and here for a comparison of lamp technologies.
LPG
Liquefied Petroleum Gas, for example propane or butane.
Luminaire
The fitting comprising reflector, lens or diffuser, and control gear, etc and lamp
Lux
Unit of illumination intensity (light flux per unit area)
LV
Low-voltage. Commonly held to signify voltages less than 440V although in some contexts indicating 12V as distinct from mains voltage

Light meter