In
thermodynamics, a
critical point (or
critical state) is the end point of a phase
equilibrium curve. The most prominent example is the liquid-vapor critical point, the end point of the pressure-temperature curve that designates conditions under which a liquid and its vapor can coexist. At the critical point, defined by a
critical temperature Tc and a
critical pressure pc,
phase boundaries vanish. Other examples include the liquid–liquid critical points in mixtures.