Critical point (Chemistry Dictionary)

Critical point : The end point of a phase equilibrium curve or pressure–temperature curve at which conditions are such that phase boundaries vanish and a substance’s different phases, such as liquid and vapor, can coexist. The critical point is defined by the intersection of a critical temperature, T_c, and a critical pressure, p_c; above this temperature and pressure, all distinction between phases disappears and the substance becomes a supercritical fluid.