Definition: A foot-candle (symbol: ft-cd) is a non-SI unit of illuminance or light intensity. It is defined as the amount of light cast by one candle on a surface one foot away. It is equal to one lumen per square foot.

History/origin: The foot-candle originated from the historical practice of measuring light intensity based on the light emitted by a standard candle. The distance was set at one foot, hence the name foot-candle. It was a common unit before the adoption of SI units.

Current use: While less common than the SI unit lux, foot-candles are still used in some industries, particularly in the United States, for specifying lighting requirements in building codes, photography, and certain scientific applications. It provides a practical and easy-to-understand measure of light intensity for certain contexts.