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Related to vapour: vapour pressure
1. particles of moisture or other substance suspended in air and visible as clouds, smoke, etc.
2. a gaseous substance at a temperature below its critical temperature
3. a substance that is in a gaseous state at a temperature below its boiling point
water vapor transmission (WVT)
The rate of water vapor flow, under steady specified conditions, through a unit area of material between the two parallel surfaces (and normal to these surfaces).