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

---

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

---

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

---

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

“With a low relative humidity and extreme temperatures, the fire environment will be capable of creating extreme fire behavior,” Cohen said.

From Los Angeles Times ● Aug. 20, 2025

Meteorologists in the US and elsewhere have expressed concerns over "reduced number of weather balloons" that observe wind, relative humidity and pressure above the ground.

From BBC ● Jul. 6, 2025

Physiological Effects of Heat and Humidity.—Tropical heat is associated with high relative humidity except over deserts and in dry seasons.

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