The humidity of air measured in percentage is called relativehumidity. There are three main measurements of humidity: relative,absolute and specific. Absolute humidity (units are grams of watervapour per cubic meter volume of air) is a measure of the actualamount of water vapour in the air, regardless of the air temperature.Relative humidity, expressed as a percent, is a measure of theamount of water vapour that air is holding compared the the amount it can hold at a specific temperature. Saturated air has a relativehumidity of 100%.Specific humidity refers to the weight of water vapour contained in a unit weight (amount) of air (expressed as grams of water vapor per kilogram of air).