| Term: | Triple point |
| Definition: | (1) The thermodynamic state at which three phases of a substance exist in equilibrium. (2) A junction point of three distinct air masses within the tropics at which cyclogenesis may occur. syn. triple state |
| Term: | Triple point |
| Definition: | The temperature, 273.16 K by definition, and pressure, 611.657 Pa, at which ice, water and water vapour are in thermodynamic equilibrium. The term 'point' derives from the practice in thermodynamics of choosing temperature and pressure as the coordinates of a two- or higher-dimensional phase diagram. |