A lip refers to the soft, fleshy edges that form the opening of your mouth. You have an upper lip and a lower lip, and together they help you eat, drink, speak, and make facial expressions. When you smile, frown, or whistle, you're using your lips.

Lips are surprisingly important. They help you form sounds when speaking: try saying “pop” or “mama” without moving your lips! They also protect your teeth and help you sense if food is too hot before you bite into it. Some animals, like horses and elephants, have especially sensitive lips they use almost like fingers to grab and explore things.

The word also appears in several common expressions. When someone tells you to button your lip, they're asking you to stop talking. Lip service means someone says the right things without actually meaning them or planning to follow through, like promising to help clean up but then disappearing. If you're biting your lip, you might be nervous or trying to keep yourself from saying something. And when someone gets lippy, they're being rude or disrespectful, usually by talking back or making smart remarks.