Fat is a soft, oily substance found in the bodies of animals and in certain plant foods. Your body needs some fat to stay healthy: it cushions your organs, stores energy for later use, and helps your brain work properly. Foods like butter, olive oil, nuts, and avocados contain fat.

In everyday language, calling someone or something fat means having extra body weight or being thick and bulky. A fat book has many pages. A fat wallet bulges with cash. When describing people, though, the word can hurt feelings, so when it is necessary to discuss someone's weight, such as in a doctor's appointment, words like “overweight” or “heavy” are often used instead.

The word also describes richness or abundance. A farmer might talk about a fat harvest when crops grow especially well. A fat paycheck means earning more money than usual.

People sometimes use “fat” in phrases like fat chance, which oddly means almost no chance at all (it's sarcastic). If someone promises you something but doesn't deliver, you might say they were just chewing the fat, meaning having a casual conversation without taking real action. And when someone lives off the fat of the land, they're enjoying the best and most abundant things available.