Interaction is what happens when two or more people, things, or forces affect each other. When you have a conversation with a friend, that's an interaction: you say something, they respond, you react to their response, and back and forth you go. When you pet a dog and it wags its tail, that's an interaction too.

The key idea is that interaction goes both ways: a genuine exchange where both sides respond and influence each other. Scientists study how chemicals interact in experiments, watching how one substance changes when mixed with another. Video game designers create ways for players to interact with the game world: pressing buttons, solving puzzles, and making choices that change what happens next.

You interact with your environment constantly, whether you're aware of it or not. When you walk on ice and slip, that's you interacting with a slippery surface. When plants grow toward sunlight, they're interacting with their environment. Some interactions are simple and quick, like catching a ball. Others are complex and ongoing, like the daily interactions between classmates that gradually build friendships or reveal personality.

Teachers often encourage student interaction because learning happens when kids talk through ideas together rather than just listening passively. The quality of your interactions with others shapes your relationships, your learning, and your experience of the world.