* Mixture: A combination of two or more substances where each substance retains its own properties.

* Compound: A substance formed when two or more elements chemically combine in a fixed ratio.

* Solution: A special type of mixture where one substance (solute) is dissolved evenly throughout another (solvent).

Humidity is the presence of water vapor in the air. Water vapor is simply water in its gaseous state. The air and the water vapor remain separate entities, even though they are mixed together.

Here's how it breaks down:

* Air: A mixture of gases (primarily nitrogen and oxygen)

* Water vapor: Gaseous water molecules

The water vapor doesn't chemically combine with the air, nor does it dissolve into the air like salt dissolves in water. It simply exists as a separate component within the air mixture.

Therefore, humidity is a mixture of air and water vapor.