- the mass of water vapor present in a unit volume of moist air.
- the humidity of the atmosphere, usually expressed as the number of grams of water contained in 1 cubic metre of airCompare relative humidity
- The weight of water vapor present per unit volume of a gas or a mixture of gases.
- The amount of water vapor that is present in a unit volume of air, usually expressed in grams per cubic meter. Absolute humidity does not fluctuate with the temperature of the air. Compare relative humidity.