The pressure exerted by the molecules of a given vapor. For a pure, confined vapor, it is that vapor's pressure on the walls of its containing vessel; for a vapor mixed with other vapors or gases, it is that vapor's contribution to the total pressure (i.e., its partial pressure). In meteorology, vapor pressure is used almost exclusively to denote the partial pressure of water vapor in the atmosphere. Care must be exercised in interpreting the term's meaning as used in other branches of science. See saturation vapor pressure, equilibrium vapor pressure.