(thermodynamics) A nonSI unit for heat energy, which is equivalent to the amount of heat needed to raise the temperature of 1 gram of water by 1 degree Centigrade at 1 atmospheric pressure.
A one small calorie is equal to 4.1840 joules. Joule (which is an SI unit) is now more preferred over small calorie (which is nonSI unit) for measuring heat energy.
Word origin: from Latin calor, heat
Compare: large calorie