1. Thermodynamics, in which a constant which expresses the number of units of heat in terms of a unit of work, typically expressed as the amount of heat transfer required to raise the temperature of one gram of water from 14.5 to 15.5 degrees centigrade.
2. The amount of mechanical energy equivalent to a unit of heat.
3. The number of units of work or energy equal to one unit of heat; such as, 4.1858 joules, which equals one small calorie.