A lesson is something you learn, either from being taught or from your own experience. In school, a math lesson might teach you how to multiply fractions, while a history lesson explores what happened during the American Revolution. Teachers plan lessons to help students understand new concepts, practice skills, or discover interesting ideas.

The word also describes what you learn from mistakes or difficult situations. When you forget your homework and lose recess time, that's a hard lesson about responsibility. When you practice piano every day and finally master a difficult piece, you've learned the lesson that persistence pays off. Parents often say “let that be a lesson to you” when they want you to remember something important from what just happened.

Sometimes people talk about learning your lesson, which means you've understood something well enough that you won't make the same mistake again. A lesson learned is wisdom gained from experience, good or bad. These lessons stick with you longer than anything you might memorize from a textbook, because you felt them yourself.