An activity is something you do, especially something that involves effort or has a purpose. When your teacher asks what activities you did over the weekend, she wants to know how you spent your time: playing soccer, reading, building with LEGO bricks, or visiting your grandparents.

Activities can be physical (like swimming or dancing), mental (like solving puzzles or writing stories), or social (like playing board games with friends). Schools often offer after-school activities like drama club, chess team, or band practice. These are organized things you can choose to do beyond regular classes.

The word suggests action and engagement. Watching TV might be something you do, but people usually call it an activity when it involves some kind of active participation or effort. Scientists might study the activity of ants in a colony, meaning all the purposeful things the ants are doing: gathering food, building tunnels, caring for eggs.

When something shows a lot of activity, it means there's plenty of action and energy happening. A quiet library has little activity, while a busy playground buzzes with it. You might also hear about volcanic activity (eruptions and lava flows) or brain activity (the electrical signals firing in your mind right now as you read this).