What is the term for an energy unit that is one-thousandth of a kilocalorie?

The term for an energy unit that is one-thousandth of a kilocalorie is a calorie. A kilocalorie, often referred to simply as a calorie in dietary contexts, is a unit of measurement for energy. Specifically, one kilocalorie is equivalent to 1,000 calories, making the calorie a smaller unit of energy commonly used in nutritional context to express the energy value of foods.

In terms of energy measurement in nutrition, it is important to understand that calories reflect the energy needed to raise the temperature of one gram of water by one degree Celsius. Therefore, when discussing nutrition and energy values, calories provide a more practical and relatable unit for everyday understanding compared to the kilocalorie, which is prominent in dietary guidelines.

The other options provided refer to different units of measurement that do not pertain to this specific context. Joules measure energy, but the relationship to kilocalories is different (1 kilocalorie is approximately 4,184 joules). Grams are a unit of mass, not energy, and watts are a measure of power, defined as energy per unit time. Hence, calorie stands out as the correct term for an energy unit that is one-thousandth of a kilocalorie.