Condensation is the process by which gas is converted from its gaseous form to its liquid form.
Condensation commonly occurs when a vapour is cooled to a liquid, but can also occur if a vapour is compressed (i.e. pressure on it is increased) into a liquid, or undergoes a combination of cooling and compression. Liquid which has been condensed from a vapour is called condensate. A device or unit used to condense vapours into liquid is called a condenser.