* Air is a mixture of gases, primarily:

* Nitrogen (N₂) - about 78%

* Oxygen (O₂) - about 21%

* Argon (Ar) - about 0.9%

* Other gases (including carbon dioxide, neon, helium, etc.) - about 0.1%

* Oxygen gas (O₂) is one of the major components of air, making up about 21% of its volume.

So, the relationship is that oxygen gas is a constituent of air, and it's essential for many life processes, including respiration.