water vapor

American  

noun

• water vapors
  plural

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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Other Word Forms

Noun Inflected Forms

• water vapors
  plural

Etymology

Origin of water vapor

First recorded in 1875–80

Example Sentences

See Examples For:

water vapor

“Believe it or not, water vapor is actually the most potent and efficient greenhouse gas.”

From Los Angeles Times ● Aug. 28, 2026

Together, the studies suggest that high water vapor supersaturation occurs in the cloud environments where condensational aerosol convective invigoration is most likely.

From Science Daily ● Aug. 1, 2026

The method captures the balance between water vapor produced as air rises and water vapor removed as it condenses onto droplets.

From Science Daily ● Aug. 1, 2026

The clouds, which have been observed during wildfires in Canada and Australia, are created by intense heat that lifts hot smoky air and causes the water vapor to condense into ash.

From The Wall Street Journal ● Jul. 29, 2026

Like Venus, the Earth also has a greenhouse effect due to its carbon dioxide and water vapor.

From "Cosmos" by Carl Sagan