Calories (nutritional)
A nutritional calorie, specifically a kilocalorie (kcal), is the amount of energy required to raise the temperature of one kilogram of water by one degree Celsius. In nutritional contexts, the term "calorie" typically refers to a kilocalorie.
Btu (mean)
Btu (mean) is a unit of energy used primarily in the United States defined as the heat required to raise the temperature of one pound of water from 59°F to 60°F under standard atmospheric pressure.