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

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

Those conditions will be particularly challenging when combined with low relative humidity, little cooling at night and a dry landscape.

From Los Angeles Times • Aug. 19, 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

“A combination of strong winds, low relative humidity, and warm temperatures can contribute to extreme fire behavior,” the weather service warned of these areas.

From Los Angeles Times • Jun. 20, 2025

The instruments used in this study were unmodified Belfort hygrothermographs containing as sensing units a hair element for relative humidity and a Bourdon tube for air temperatures.

From Comparative Ecology of Pinyon Mice and Deer Mice in Mesa Verde National Park, Colorado by Douglas, Charles L.