Colour Temperature - Colour temperature describes whether a light source appears "warm" or "cool" - indicated by the correlated colour temperature (CCT). Lamps with a warm appearance have a CCT of 2007-3000K, and are considered appropriate for domestic settings; cooler lamps might be 4000K, and are used more often in offices and retail. The higher the colour temperature, the "cooler" the appearance.

CRI - Short for colour-rendering-index, CRI is the ability of a light source to show the colours of objects properly. Lamps with poor colour rendering will distort some colours, which may mean you end up with brown socks when you wanted green ones. The higher the CRI, on a 0-100 scale, the more accurately the lamp will show colours.

CE Mark - Standing for Communaté Européene, the CE mark is the symbol that must be stamped on lighting products (and other goods) for them to be sold legally in the European Economic Area. It's how manufacturers declare that their products comply with all relevant EU legislation.

Circuit watts - Circuit watts (W) means the number of watts used to power an entire circuit, rather than just a luminaire.

kWh - The kilowatt-hour is a unit of energy equal to 1,000 watt-hours. That's what a 1,000W device used in one hour - or what a 1W device uses in 1,000 hours. It's the unit that your electricity bill is counted in.

Constant current driver - Constant current drivers are electronic components that are used with LED luminaires. Their purpose is to maintain a constant current to the LED's (in contrast , a transformer maintains a constant voltage). Drivers can be built into the luminaire or mounted remotely, and they often incorporate other functions such as dimming.

Lux - Lux is the international unit of illuminance - a measure of how much luminous flux (in lumens) is spread over a given area (in square metres). In other words, it tells you how much light is arriving at a surface. 1lm/m²equals 1 lx. Multiply an illuminance figure in lux by an amount of time in hours and you have a measure of exposure in lux hours - useful if you are looking after delicate objects or surfaces that can't be exposed to too much light.