Life is the quality that separates living things from non-living things. A squirrel running up a tree, a rose growing in a garden, and you reading this sentence all share something remarkable: you're alive. Living things grow, need energy, respond to their surroundings, and can create more living things like themselves. A rock doesn't do any of these things, so it isn't alive.

Scientists define life through these key features: living things are made of cells, they use energy, they grow and develop, they respond to their environment, and they reproduce. Even the tiniest bacterium and the largest whale share these characteristics.

The word also means the period between birth and death. You might talk about events in your life, like learning to ride a bike or starting middle school. Someone's life story includes everything that happened to them from beginning to end. When we say something happened in real life, we mean it actually occurred, not in a story or in your imagination.

Life can also mean energy and excitement. A party full of laughter and games has life to it. A dull party might need someone to bring it to life. When a teacher makes history come to life, they make it feel vivid and real instead of just names and dates.

People also use life to describe a particular way of living, like farm life or city life.