Definition - What does Vapor Phase mean?
Vapor Phase is a state in which a liquid is converted into a gaseous state at a certain temperature. The temperature of the material is lower than its critical temperature and if the pressure on the vapor is increased, i.e., when the temperature is reduced, the vapor can be condensed and converted into liquid phase.
Petropedia explains Vapor Phase
A liquid in vapor phase can be liquefied by compression alone without cooling. It is one of the distinct forms that matter takes. If we consider an example of water, it has a critical temperature of 647 Kelvin, which is the highest temperature at which liquid water can exist. In the atmosphere at ordinary temperatures, therefore, gaseous water (known as water vapor) will condense into a liquid if its partial pressure is increased sufficiently. Water vapor is lighter than air and can be produced by the sublimation of ice or evaporation of liquid water.