Humidity is the amount of water vapor present within air, while air itself is a mixture of various gases. Think of it this way: air is the container, and humidity is one of the things inside the container.
Here's a more detailed breakdown:
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Air: Air is primarily composed of nitrogen (about 78%), oxygen (about 21%), argon (about 0.9%), and other trace gases, including carbon dioxide. It's the gaseous substance that surrounds the Earth and that we breathe. It exists regardless of whether any water vapor is present.
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Humidity: Humidity refers specifically to the concentration of water vapor within that air. Water vapor is the gaseous form of water and is invisible to the naked eye. High humidity means there's a large amount of water vapor in the air, making it feel damp. Low humidity means there's little water vapor, making the air feel dry.
Essentially, humidity is a component of air, not something separate from it.
| Feature | Air | Humidity |
|---|---|---|
| Definition | Mixture of gases (N2, O2, Ar, etc.) | Concentration of water vapor in the air |
| Composition | Various gases | Water in gaseous form (H2O) |
| Visibility | Generally invisible | Invisible (but its effects are felt) |
| Variability | Relatively stable composition | Highly variable depending on temperature and pressure |
| Effect | Supports life, enables breathing | Impacts comfort, weather patterns |
In short, you can have air without humidity (completely dry air, though rare), but you can't have humidity without air because humidity is water vapor present in the air.
