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

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Etymology

Origin of water vapor

First recorded in 1875–80

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Example Sentences

See Examples For:

water vapor

When leaves release water vapor through their stomata, they start the process of evapotranspiration, which draws water up to the tallest part of a plant, like a beverage being sucked through a straw.

From The Wall Street Journal ● Oct. 16, 2026

Essentially, cloud seeding speeds up the natural process of water vapor condensing inside of clouds.

From BBC ● Oct. 7, 2026

In the simulations, exposing Earth's atmosphere to a dense, cold cloud of galactic hydrogen increased atmospheric water vapor and changed conditions in the upper atmosphere.

From Science Daily ● Sep. 2, 2026

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

From Los Angeles Times ● Aug. 28, 2026

If Venus were soaking wet, it should be easy to see the water vapor lines in its spectrum.

From "Cosmos" by Carl Sagan

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