Respiration is the process of breathing, where living things take in oxygen and release carbon dioxide. When you inhale, air flows into your lungs, and tiny blood vessels absorb the oxygen your body needs to turn food into energy. When you exhale, you push out carbon dioxide, a waste product your body doesn't need.

You can observe your own respiration by placing a hand on your chest and feeling it rise and fall with each breath. During exercise, your respiration rate increases because your muscles need more oxygen to keep working. When you're sleeping or resting quietly, you breathe more slowly because your body needs less energy.

Scientists use the word respiration in a broader way too. Cellular respiration describes the chemical process that happens inside every cell of your body, where oxygen combines with nutrients from food to create energy. This process keeps you warm, helps you think, and powers every movement you make. Even plants perform respiration, though they also make their own food through photosynthesis. Without respiration, no animal or plant could survive, because there would be no way to convert food into usable energy.