What is Air ?
Air is (noun) 1. a mixture of gases, mainly oxygen and nitrogen, which cannot be seen, but which is all around us and which every animal breathes His breath was like steam in the cold air. He threw the ball up into the air. 2. a method of travelling or sending goods using aircraft 3. a little tune She played an air by Bach. 4. an appearance or feeling There was an air of gloom over the meeting. (verb) to freshen a room or clothes by giving them more air Let’s open the windows to air the room.
source: Easier English, Student Dictionary Upper Intermediate Level