Vapor Pressure

The pressure exerted by a vapor in thermodynamic equilibrium with its condensed phase(s) at a given temperature in a closed system; commonly called the equilibrium (or saturated) vapor pressure for a pure substance.

The equilibrium pressure exerted by a substance's vapor when it is in thermodynamic equilibrium with its condensed phase (liquid or solid) at a given temperature; for a pure component this is the saturation pressure p_sat(T), expressed as a function of temperature and the substance's thermodynamic properties.