Air is composed of matter. Air is gas, so it is composed of molecules that are spread far apart from each other.
The definition of matter is something that takes up space (has volume) and has mass (weight). Matter is generally a solid, liquid or a gas, though scientists have determined that plasma and Bose-Einstein condensates are also states of matter. Air is a gas, and it both takes up space and has mass. Air is composed of oxygen, nitrogen and argon, as well as a few other smaller elements. Oxygen makes up the biggest percentage of air at 78 percent, while nitrogen makes up about 21 percent and argon only makes up about 1 percent.