water vapor

American  

noun

1. a dispersion, in air, of molecules of water, especially as produced by evaporation at ambient temperatures rather than by boiling.

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water vapor Scientific  

1. Water in its gaseous state, especially in the atmosphere and at a temperature below the boiling point. Water vapor in the atmosphere serves as the raw material for cloud and rain formation. It also helps regulate the Earth's temperature by reflecting and scattering radiation from the Sun and by absorbing the Earth's infrared radiation.

2. See also vapor

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Etymology

Origin of water vapor

First recorded in 1875–80

Example Sentences

One early idea was that more snow might be turning directly into water vapor, a process called sublimation.

From Science Daily • Apr. 14, 2026

Ajami pointed out that extreme heat is not only causing snow to melt faster but is also causing sublimation, in which snow is transformed directly to water vapor.

From Los Angeles Times • Mar. 15, 2026

That storm turned water vapor into ice at natural gas wellheads, blocking fuel production.

From Barron's • Jan. 21, 2026

Leaf Gas Exchange Measurement Highly sensitive instruments track exactly how much CO2 the leaf absorbs and how much water vapor it releases.

From Science Daily • Jan. 7, 2026

Its air is thin, containing mostly carbon dioxide but also some molecular nitrogen and argon and very small quantities of water vapor, oxygen and ozone.

From "Cosmos" by Carl Sagan