Water vapor is the gaseous form of water in temperatures above 100 degrees Celsius (the boiling point of water). Once the temperature goes below 100 degrees Celsius, then water vapor reverts back to its liquid form and the process is called condensation. In extremes of temperatures such that when temperature goes below 0 degrees Celsius (the freezing point of water), water vapor can crystallize and form ice without condensing back to water first. This process is called deposition.