Any of several approximately equal units of heat, each measured as the quantity of heat required to raise the temperature of one (1) gram of water by 1°C from a standard initial temperature, specially from 3.98°C, 14.5°C, or 19.5°C, at a constant pressure of one (1) atmosphere. Also called “gram calorie”, “small calorie”.The unit of heat equal to 1/100 the quantity of heat required to raise the temperature of one (1) gram of water from 0°C to 100°C at one (10 atmosphere pressure. Also called “mean calorie”.The unit required to raise the temperature of one (1) Kilogram of water by 1°C at one (1) atmosphere pressure. Also called “kilogram calorie”, “large calorie”.