from the GNU version of the Collaborative International Dictionary of English
- n. the quantity of heat required to raise, by one degree, the temperature of a unit mass of water, initially at a certain standard temperature. The temperature usually employed is that of 0° Centigrade, or 32° Fahrenheit.
- n. a determinate quantity of heat adopted as a unit of measure; a thermal unit (see under Thermal). Water is the substance generally employed, the unit being one gram or one pound, and the temperature interval one degree of the Centigrade or Fahrenheit scale. When referred to the gram, it is called the gram degree. The British unit of heat, or thermal unit, used by engineers in England and in the United States, is the quantity of heat necessary to raise one pound of pure water at and near its temperature of greatest density (39.1° Fahr.) through one degree of the Fahrenheit scale.
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