Fr.: humidité absolueIn a system of moist air, the ratio of the mass of water vapor to the total volume of the system. → humidity. Humidity, from O.Fr. humide, from L. humidus "moist, wet," variant (by influence of humus "earth") of umidus, from umere "be moist. "Nam "humidity, moisture," from Mid.Pers. nam, namb "moisture;" Av. napta- "moist," nabās-câ- "cloud," nabah- "sky;" cf. Skt. nábhas- "moisture, cloud, mist;" Gk. nephos "cloud, mass of clouds," nephele "cloud;" L. nebula "mist," nimbus "rainstorm, rain cloud;" O.H.G. nebul; Ger. Nebel "fog;" O.E. nifol "dark;" from PIE *nebh- "cloud, vapor, fog, moist, sky." Fr.: humidité relativeThe amount of moisture in the air compared to what the air can "hold" at that temperature. It is given by the ratio of the partial pressure of water vapor in the mixture to the saturated vapor pressure of water at a specific temperature. Fr.: humidité spécifiqueThe dimensionless ratio of the mass of water vapor to the total mass in a particular volume. → humidity