A unit of illumination is a measure of the amount of light emitted from a source. The most common units of illumination are lux (3 letters), lamberts (7 letters), phot (4 letters), lumen (5 letters), candela (7 letters) and CANDLE (6 letters). Lux is a unit of illumination that measures the amount of light that falls on a surface, while lamberts measure the brightness of a light source. Phot is a unit of illumination that measures the amount of light emitted from a source, while lumen measures the total amount of visible light emitted from a source. Candela measures the intensity of light in a particular direction, while CANDLE measures the amount of light emitted from a CANDLE.