# Relative humidity of air

Relative humidity (RH or $\Phi$) is the ratio of the partial pressure of water vapor to the equilibrium vapor pressure of water at a given temperature. Relative humidity depends on temperature and the pressure of the system of interest. The same amount of water vapor results in higher relative humidity in cool air than warm air.

Symbol
$\Phi_{air}$
Unit
$\%$
Related
$\theta_{air}$