Dampness, especially that of the air. / The amount of water vapour in the air.

plural of humidity

humidity

Containing perceptible moisture (usually describing air or atmosphere); damp; moist; somewhat wet or watery.

comparative form of humid: more humid

The ratio of the mass of water vapour to mass of air.

(meteorology) The ratio of the actual amount of water vapor (absolute humidity) present in the air to the saturation point at the same temperature, usually expressed as a percentage.

(meteorology) In a system of moist air, the ratio of the mass of water vapor present to the volume occupied by the mixture, that is, the density of the water vapor component. Absolute humidity is usually expressed in grams of water vapor per cubic meter or, in engineering practice, in grains per cubic foot. Because this measure of atmospheric humidity is not conservative with respect to adiabatic expansion or compression, it is not commonly used by meteorologists. (Also called vapor concentration and vapor density). See relative humidity.

plural of humid heat

the heat capacity (specific heat) of humid air, expressed per unit mass of dry air in the mixture. The engineering symbol is cₛ.