The dew-point temperature ( Td ) of a moist air sample, commonly termed simply the dew-point , is that temperature to which the air must be cooled in order that it shall be saturated with respect to water at its existing pressure and humidity.

The temperature at which cooled air, with no change in pressure or amount of water vapor, becomes completely saturated and forms visible condensation (attains a relative humidity of 100%).

(Dewpoint Temperature) Temperature to which a volume of air must be cooled at constant pressure and constant moisture in order to reach saturation; any further cooling causes condensation.