Condensation is the process in which water vapor in the air turns into liquid water. The opposite of condensation is evaporation, which is the process in which liquid water turns into water vapor. Condensation occurs when the air is saturated with water vapor and there is a surface for the water vapor to condense on. The most common example of condensation is when water vapor in the air condenses on a cold surface, such as a window pane or a glass of cold water.