This article is about the unit of energy. For its use in nutrition and food labeling regulations, see the article on food energy. The calorie is a pre-SI unit of energy, in particular heat. In most fields, its use is archaic, and the SI unit of energy, the joule, has become accepted. However, it remains in common use as a unit of food energy. It was first defined by Professor Nicolas Clément in 1824 as a kilogram-calorie, and this definition entered French and English dictionaries between… (More on Calories)