Dew point is the temperature at which the partial vapor pressure of water equals its saturated vapor pressure. This is the temperature at which a certain volume of air must be cooled under constant pressure and humidity to saturate it.
Dew point

Dew point is the temperature at which the partial vapor pressure of water equals its saturated vapor pressure. This is the temperature at which a certain volume of air must be cooled under constant pressure and humidity to saturate it.