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

"Enceladus itself is a key driver of this environment, releasing huge amounts of water vapor that gets ionized, loading the magnetosphere with heavy plasma that is then pulled around as the planet spins."

From Science Daily • Apr. 3, 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

Each year, wildfires burn through vast areas of vegetation, sending a complex mixture of water vapor, ash, and carbon-based chemicals into the atmosphere.

From Science Daily • Jan. 7, 2026

Theoretically, there could have been some production of oxygen by photodissociation of water vapor in ultraviolet light, but not much.

From "The Lives of a Cell" by Lewis Thomas