Condensation

The process by which vapour molecules reform a liquid; phase change from gas to liquid state.

When a moisture laden gas comes in contact with a cooler surface a change of state from gaseous to liquid occurs e.g. when you breath onto a cold pane of glass the water vapour in your breath condenses onto the glass.

Condensation is the opposite process of evaporation.

See also: Evaporation, Phase Change.