Water in gaseous form. It is one of the most import constituents of the atmosphere. Due to its molecular content, air containing water vapor is lighter than dry air. This contributes to the reason why moist air has a tendency to rise.
WATER VAPOR (H2O)
Meaning of WATER VAPOR (H2O) in English
Weather and meteorology English vocabulary. Английский словарь погоды и метеорологии . 2012