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

See Examples For:

relative humidity

The heat index is what the temperature feels like to the human body when relative humidity is combined with the air temperature.

From BBC ● Jul. 2, 2026

These included educational attainment, median household income, racial composition, average temperature and relative humidity, smoking prevalence, BMI, and distance to the nearest hospital.

From Science Daily ● Feb. 24, 2026

But temperatures have dipped and relative humidity has climbed, instilling hope for the trees — and turning a corner on the blaze.

From Los Angeles Times ● Sep. 5, 2025

Those winds could be more concerning given otherwise hot and dry weather, with temperatures around the fire expected to reach into the low 90s Thursday, and relative humidity dropping to 20% or lower.

From Los Angeles Times ● Aug. 14, 2025

The main things influencing evaporation are, first, the quantity of heat supplied and, second, the relative humidity of the immediately surrounding space.

From Seasoning of Wood by J. B. (Joseph Bernard) Wagner