The temperature at which all the physical states of matter are coexists is called critical temperature.

The temperature above that the gas can not be liquefied is called critical temperature of that gas.Gases with high critical temperature are liquefied easily.

the critical temperature of oxygen is -118.6 C/ -155 F

The critical pressure of a substance is the pressure required to liquefy a gas at its critical temperature. Some examples are shown below.

The critical temperature of gasoline is the temperature at which it becomes combustible and varies according to the pressure the gas is under. On average this temperature is 241 degrees Celsius.

A pseudo-critical substance is a mixture of two or more fluids at their joint critical pressures. A critical fluid is a fluid at its critical pressure and temperature. At this point, it is no longer possible to distinguish between gas and liquid, due to the high pressure and temperature.