A measure of energy content frequently used in nutrition. The term Calorie is frequently used synonymously with kilocalorie although strictly speaking it should be capitalized. The prefix "kilo" means 1,000. Thus, one kilocalorie (abbreviated kC.) is the amount of heat required to increase the temperature of 1,000 g of water by 1 degree C. while a calorie (small c.) refers to heating 1 g of water by 1 degree C. The caloric content of foods and daily energy requirements are given in kilocalories. A small calorie is one-thousandth of a kilocalorie. However, the international standard for energy content is based on the Joule; 1 kilocalorie equals 4.18 kilojoules.
(Encyclopedia of Nutrition and Good Health by Robert Ronzio)