From the Latin noun calor meaning "heat," a calorie is technically defined as "the heat required to raise one gram of water one degree Celsius." Because this is such a small amount of heat, most of us use the word calorie to refer to what is actually a kilocalorie, or "the heat required to raise one kilogram of water one degree Celsius." Calories are essentially the measure of how much energy (or heat) various foods can produce. For this reason, the "calorie count" on food packaging labels actually lists the number of kilocalories (not calories) it has, because learning that a Twinkie has 260 (kilo)calories is far more inviting than listing that it has 260,000 calories.