Calorie

Etymology

From French "calorie," from Latin "calor" (heat). It entered science as a unit of heat energy — the heat needed to warm water — and only later migrated to nutrition. The food "Calorie" is technically a kilocalorie, a thousand of the original units.

noun · /KAL-uh-ree/
A unit measuring the energy that food supplies or the body spends.
What it names
Reach for it when you mean the energy content of food — a measurement, not an ingredient or substance you can point to.
Example
A gram of fat carries more than twice the calories of a gram of protein.
Related idea
A calorie measures energy; a nutrient is the actual substance — protein, vitamin, mineral. Vitamins have zero calories yet are essential, and alcohol has calories but almost no nutrients, which is why "empty calories" names food that fuels without nourishing.