ETYM Old Eng. vapour, Old Fren. vapour, vapor, vapeur, French vapeur, Latin vapor. Related to Vapid.
Fine separated particles floating in the air and clouding it. A substance in the gaseous state.
(Alternate spelling: vapour).
A visible suspension in the air of particles of some substance; SYN. vapour.
One of the three states of matter (see also solid and liquid). The molecules in a vapor move randomly and are far apart, the distance between them, and therefore the volume of the vapor, being limited only by the walls of any vessel in which they might be contained. A vapor differs from a gas only in that a vapor can be liquefied by increased pressure, whereas a gas cannot unless its temperature is lowered below its critical temperature; it then becomes a vapor and may be liquefied.