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

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

From Barron's • Jan. 21, 2026

At the same time, a warmer atmosphere holds more water vapor, which is then released in fewer, more extreme rainstorms.

From Los Angeles Times • Jan. 9, 2026

These microscopic pores act like adjustable valves, letting carbon dioxide enter the leaf for photosynthesis while allowing water vapor to escape into the air.

From Science Daily • Jan. 7, 2026

The tower is bristling with high-tech instruments - sensors that track almost everything happening between the forest and the atmosphere: water vapor, carbon dioxide, sunlight, and essential nutrients like nitrogen and phosphorus.

From BBC • Nov. 16, 2025

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

From "Cosmos" by Carl Sagan