a basic unit of luminous intensity in the International System of Units (SI), formally defined as the luminous intensity of a source that emits monochromatic radiation of frequency 540 × 10 12 hertz and that has a radiant intensity of 1/683 watt/steradian: adopted in 1979 as the international standard of luminous intensity.
For historical reasons, the candela is the fundamental unit of light, even though the lumen is more simply defined.
British Dictionary definitions for candela
the basic SI unit of luminous intensity; the luminous intensity in a given direction of a source that emits monochromatic radiation of frequency 540 × 1012 hertz and that has a radiant intensity in that direction of (1/683) watt per steradian cd Also called candle, standard candle
C20: from Latin: candle
Felix. 1910–97, Mexican architect, noted for his naturalistic modern style and thin prestressed concrete roofs
candela can·del·a (kān-děl'ə) n. Abbr. cd A unit of measurement of luminous flux, equal to the amount of light given out through a solid angle by a source of one candela radiating equally in all directions. Also called candle.
(kān-děl'ə) The SI unit used to measure the brightness of a source of light (its luminous intensity). By definition, one square centimeter of a blackbody at the freezing point of platinum emits one-sixtieth of a candela of radiation. See Table at measurement. See also lumen, luminous flux.