• The fundamental SI unit of luminous intensity. Formerly, it was defined in various manners, ranging from the light of a certain type of candle under particular conditions, to more recently as a given proportion of the radiating power of a blackbody under specific conditions. It is currently defined as the luminous intensity of a light source emitting monochromatic radiation in a given direction at a frequency of 540 terahertz, with a power of 1/683 watt per steradian in the specified direction. Its symbol is cd. This term was formerly known as candle, international candle, standard candle, or new candle.

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