Up is a direction that goes away from the ground toward the sky. When you climb stairs, you go up. When a balloon floats away, it goes up. When you look at clouds or stars, you look up.

The word also describes position or location. If something is up on a shelf, it sits higher than where you're standing. When the sun is up, it has risen above the horizon. When you say “I'll be up in my room,” you mean you're on a higher floor.

Up can mean increasing or improving. Prices go up when they get more expensive. The volume goes up when you turn it louder. When your grades go up, they improve. Athletes try to keep their performance up.

The word appears in countless phrases that don't directly relate to direction. When time is up, it has run out. When you own up to a mistake, you admit it. When you look up a word, you search for it in a dictionary. When you make up a story, you invent it. When someone says “What's up?” they're asking how you're doing. When you give up, you stop trying. When you speak up, you talk louder or share your opinion.

Up is one of the most flexible and useful words in English, appearing in hundreds of expressions that native speakers learn naturally over time.