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(Science: physics, unit) The si unit of luminous intensity, 1 lumen per m2; the luminous intensity, in a given direction, of a source that emits monochromatic radiation of frequency 540 x 1012 hertz and that has a radiant intensity in that direction of 1/683 watt per steradian (solid angle).

Synonym: candle.

Abbreviation: cd

Origin: L.