In thermodynamics, the triple point of a substance is the temperature and pressure at which the three phases of that substance coexist in thermodynamic equilibrium. It is that temperatureand pressure at which the sublimation curve, fusion curve and vaporisation curve meet.
At the triple point, all three phases (solid, liquid, and gas) are in equilibrium. Since the triple point is a point, there is only one temperature and one pressure where the three phases will exist. This fact often helps in identifying compounds or in problem solving.
