The SI unit of luminous intensity which is one of the seven fundamental SI units. It is defined as the luminous intensity n a given direction of a source that emits monochromatic radiation of frequency 540 THz and that has a radiant intensity in that direction of 1/683 watts per sterradian. The candela is abbreviated "cd."

The lumen is defined as 1 cd sterradian, and the lux is defined as 1 cd sterradian m^-2.

Candle, Lumen, Luminous Intensity, Lux, Radiant Intensity