Calorie

Definition:

In technical terms, a calorie is the amount of energy it takes to raise the temperature of a gram of water by one degree celsius. ^[1]

In the context of nutrition, though, it’s usually shorthand for a kilocalorie (kcal), which is actually equal to 1,000 calories, or the amount of energy required to raise the temperature of a litre of water by one degree. Most adults should aim to consume 2,000-2,500 kcal a day. ^[1]