humidity

Etymology

It is inherited from Middle English humidite, borrowed from Old French humidité (“dampness”),^[2][3][4] from Latin hūmiditās (“moisture”),^[3][5] from hūmidus (“moist, wet”).^[2][3] The AHD calls the Latin noun Medieval Latin, and Merriam-Webster Late Latin;^[2][6] the Oxford Dictionary of English allows a borrowing from either French or Latin.^[7] In Anglo-Norman the noun was recorded in the early 13th century as one of the four qualities associated with the humours.^[8]

Earliest recorded meaning

In the plural, the humours and juices of animals and plants, about 1400, in Lanfranc's Cirurgie.^[4]

Semantic evolution

Lydgate used it in 1412–20 for moisture itself, the fluid that makes something damp,^[4][9] and by about 1450 it meant the quality or condition of being damp.^[4][9] Johnson (1755) defined it as the power of wetting other bodies.^[10] The modern meteorological sense, a measure of the moisture in the air compared with the amount that would saturate it, dates from 1820; the full phrase relative humidity is recorded by 1819.^[3] Meteorologists also speak of absolute humidity, the mass of water vapour in a given volume of air.^[11][12]

Timeline

• c. 1400 – plural, humours and juices of animals and plants.^[4]
• 1412–20 – moisture, damp (Lydgate).^[4]
• c. 1450 – the condition of being damp.^[4]
• 1755 – Johnson defines it as the power of wetting other bodies.^[10]
• 1819 – relative humidity.^[3]
• 1820 – a measure of moisture in the air.^[3]

Modern meaning

Noun

1. Dampness, especially of the air.
2. The amount of water vapour in the air; relative humidity.

Word family

• absolute humidity
• relative humidity
• specific humidity

Related words

• humid
• humidifier
• humidify

References

1. ^ a b Wiktionary, the free dictionary, https://en.wiktionary.org
2. ^ a b c The American Heritage Dictionary of the English Language (online 2024), 5th ed., Boston: Houghton Mifflin Harcourt
3. ^ a b c d e f Harper, Douglas. Online Etymology Dictionary, https://www.etymonline.com
4. ^ a b c d e f g Oxford English Dictionary Online (accessed March 2026), Oxford: Oxford University Press
5. ^ Klein, Ernest. A Comprehensive Etymological Dictionary of the English Language. 2 vols. Amsterdam: Elsevier, 1966–1967.
6. ^ Merriam-Webster Unabridged Dictionary (2024), online ed., Springfield, Mass.: Merriam-Webster
7. ^ Stevenson, Angus, ed. (2010), Oxford Dictionary of English, 3rd ed., Oxford: Oxford University Press
8. ^ Anglo-Norman Dictionary (AND2), Aberystwyth University, anglo-norman.net (2nd ed., 2005–)
9. ^ a b Kay, Christian; Roberts, Jane; Samuels, Michael; Wotherspoon, Irené, eds. (2009), Historical Thesaurus of the Oxford English Dictionary, Oxford: Oxford University Press; online edition (2024)
10. ^ a b Johnson, Samuel (1755), A Dictionary of the English Language, London; 4th ed. 1773; Johnson's Dictionary Online, ed. Beth Rapp Young et al.
11. ^ Shorter Oxford English Dictionary on Historical Principles (2002), 5th ed., ed. William R. Trumble and Angus Stevenson, Oxford: Oxford University Press
12. ^ Collins English Dictionary (2023), Glasgow: HarperCollins