Air is the invisible mixture of gases that surrounds Earth and fills your lungs with every breath. You can't see it, but you can feel it when wind blows against your face or when you wave your hand quickly through it. Air is mostly nitrogen and oxygen, with small amounts of other gases mixed in.

Every living thing on Earth depends on air. Animals breathe in oxygen from the air and use it to power their bodies. Plants take in carbon dioxide from the air and use sunlight to turn it into food, releasing oxygen back into the air in an amazing cycle that helps keep our planet alive.

Air does much more than sustain life. It carries sound waves so we can hear each other talk and sing. It creates weather patterns, from gentle breezes to powerful hurricanes. Air pressure pushing down on us from above is so strong that it would crush us if we didn't have air inside our bodies pushing back with equal force.

The word also describes a quality or feeling that someone projects. A person might put on airs, meaning they act superior or pretentious. Someone confident might have an air of authority. When you're walking on air, you're so happy you feel like you're floating.