Definitions for "Water vapour"
The most abundant greenhouse gas, water vapour is the water present in the atmosphere in gaseous form. Water vapour is an important part of the natural greenhouse effect. While humans are not significantly increasing its concentration, water vapour contributes to the enhanced greenhouse effect because the warming influence of greenhouse gases leads to a positive water vapour feedback. In addition to its role as a natural greenhouse gas, water vapour plays an important role in regulating the temperature of the planet because clouds form when excess water vapour in the atmosphere condenses to form ice, water droplets and precipitation. (Source: Government of Canada Climate Change Site, Glossary of Climate Change Terms)
Single water molecules in the air, acting as an atmospheric gas. Steam.
Water as tiny invisible droplets which may form clouds and mist
Keywords:  evaporated, air
Water that has evaporated into the air.
Keywords:  cycle, see
See "Water cycle."