Humidity and hygrometry

temperature at which air becomes saturated with water vapour

Psychrometrics (or psychrometry, ; also called hygrometry) is the field of engineering concerned with the physical and thermodynamic properties of gas-vapor mixtures.

temperature of dry air parcels that have a total pressure and density equal to a moist parcel of air

A humidistat or hygrostat is an electronic device analogous to a thermostat but which responds to relative humidity, not temperature. A typical humidistat is usually included with portable humidifiers or dehumidifiers. It can also be included with combined air cleaner or humidifier units to control a home's humidity level or any other indoor space.