relative humidity

American  

noun

1. the amount of water vapor in the air, expressed as a percentage of the maximum amount that the air could hold at the given temperature; the ratio of the actual water vapor pressure to the saturation vapor pressure. RH, rh

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relative humidity British  

noun

1. the mass of water vapour present in the air expressed as a percentage of the mass that would be present in an equal volume of saturated air at the same temperature Compare absolute humidity

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relative humidity Scientific  

1. The ratio of the actual amount of water vapor present in a volume of air at a given temperature to the maximum amount that the air could hold at that temperature, expressed as a percentage. Warm air can hold more water vapor than cool air, so a particular amount of water vapor will yield a lower relative humidity in warm air than it does in cool air.

2. Compare absolute humidity

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Etymology

Origin of relative humidity

First recorded in 1810–20

Compare meaning

How does relative-humidity compare to similar and commonly confused words? Explore the most common comparisons:

• relative humidity vs. absolute humidity
• specific humidity vs. relative humidity

Example Sentences

Relative humidity Tuesday morning was less than 5% in the area of the fire — extraordinarily dry.

From Los Angeles Times • Dec. 10, 2024

Relative humidity, which is a term for how much water vapor is actually in the air, appears to be a contributing factor.

From Salon • Nov. 10, 2021

Relative humidity measures dropped as low as 6%.

From Seattle Times • Sep. 13, 2020

Relative humidity is related to the partial pressure of water vapor in the air.

From Textbooks • Aug. 12, 2015

Relative humidity varies greatly, and very low readings have often been recorded.

From Encyclopaedia Britannica, 11th Edition, Volume 6, Slice 5 "Clervaux" to "Cockade" by Various