What does humidity mean?
Humidity is the amount of water vapour in the air, especially when expressed as a percentage of the maximum amount the air could hold at that temperature. It is commonly associated with warm, muggy weather, but high humidity can occur in cold conditions as well. High humidity slows the evaporation of sweat, which can make warm weather feel hotter and more uncomfortable, while low humidity can dry the skin and irritate the respiratory system. Meteorologists often report relative humidity because the air’s capacity to hold moisture rises with temperature. In everyday speech, the word can also refer more generally to dampness, as when someone complains about the humidity in a room. The related adjective humid describes moist air or objects, while a humidifier is a device that adds moisture to the air.
nounThe amount of water vapour in the air, especially relative to the maximum amount the air can hold at a given temperature. It may also refer more generally to dampness.
- The amount of water vapour in the air, particularly in relation to the amount the air can hold at a given temperature.
- The condition of being moist or damp.
"High humidity can make the summer feel considerably hotter."
"The relative humidity in the afternoon reached 90 percent."
"Visitors complained about the humidity inside the old greenhouse."
The plural is uncommon and is used chiefly when referring to different humidity levels or measurements.
"The sensors recorded different humidities across the two rooms."
Humidity can make a hot day feel hotter by slowing the evaporation of sweat from your skin.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Where does humidity come from?
Humidity entered English in the early 17th century from Latin humiditas, a noun formed from humidus, meaning “moist” or “damp.” The Latin adjective developed from the earlier root humus, meaning “earth,” through the notion of ground that is naturally moist. The related English forms humid, humidify, and humidifier were derived from the same Latin source.
Related word forms
How humidity is actually used
In everyday use, humidity usually refers specifically to moisture in the air. It is commonly quantified by relative humidity, the ratio of the water vapour present to the maximum the air can hold at the same temperature and pressure.
Easily confused with humidity
Humidity is the noun naming a condition or measurable amount of atmospheric moisture, while humid is the adjective describing something that is damp or moist.
Humidity is the moisture present in the air, whereas a humidifier is a device that adds moisture to a room.