SI luminosity intensity measure. Symbol: cd.
It is one of the base units in SI, and it is currently defined as
follows: the Candela is the luminous intensity, in a given direction,
of a source that emits monochromatic radiation of frequency 540*10^12
Hertz and that has a radiant intensity in that direction of 1/683
Watt per Steradian.
the basic unit of luminous intensity adopted under the System International d'Unites; equal to 1/60 of the luminous intensity per square centimeter of a blackbody radiating at the temperature of 2,046 degrees Kelvin