The base unit of luminous intensity in the International System of Units that is equal to the luminous intensity in a given direction of a source which emits monochromatic radiation of frequency 540 x 10¹² hertz and has a radiant intensity in that direction of 1/683 watt per unit solid angle -- called also candle; abbreviation cd .

烛光(光强度单位；符号: cd)。一烛光等于频率 540×10¹² 赫之光源发出之单色辐射，在一定方向每立弪之放射强度为 1/683 瓦特之发光强度。