acidity

Etymology

It is borrowed from French acidité, recorded in Middle French in 1545,^[2][3][4][5] or directly borrowed from Late Latin aciditās (“sourness; an acidic substance”), a 5th-century word,^[2][3][6][7] formed from Latin acidus (“sour, tart”) with the suffix -tās.^[2][3][5] The Latin adjective is from aceō (“to be sour, be sharp”), from Proto-Indo-European *ak- (“to be sharp”).^[3]

Earliest recorded meaning

Sourness, the quality of being acid in taste or chemically: 1615, in H. Crooke's Mikrokosmographia;^[2][5] Etymonline dates it to the 1610s.^[3]

Semantic evolution

The noun is recorded slightly earlier than the adjective acid, which Etymonline dates to the 1620s.^[2][3] The medical sense, a condition with too much acid in the body, later especially in the stomach, appears in 1682 in N. Grew;^[2] the Shorter Oxford dates the stomach sense to the mid 18th century.^[6] The figurative sense, sharpness of tone or manner, followed in 1687.^[2] Johnson (1755) defined the word as "the quality of being acid; an acid taste; sharpness; sourness".^[8] In chemistry the word came to mean the degree to which a substance is acid, often expressed as pH.^[2][9]

Timeline

• 1615 – sourness, the quality of being acid.^[2][5]
• 1682 – an excess of acid in the body, later especially the stomach.^[2]
• 1687 – figurative, sharpness of tone or demeanour.^[2]

Meanings

Noun

1. The quality or state of being acid or sour: the acidity of green apples.^[5][9][2]
2. The amount of acid in a solution, often given in terms of pH.^[9][2]
3. Hyperacidity, especially of the stomach.^[9][5][2]
4. Tartness in the taste of wine from its fruit acids.^[5]
5. Sharpness of manner or tone; tartness: The reply came with a touch of acidity.^[5][2][6]

Word family

• anacidity
• hyperacidity
• hypoacidity
• nonacidity
• superacidity

Related words

• acid

References

1. ^ Wiktionary, the free dictionary, https://en.wiktionary.org
2. ^ a b c d e f g h i j k l m n o Oxford English Dictionary Online (accessed March 2026), Oxford: Oxford University Press
3. ^ a b c d e f Harper, Douglas. Online Etymology Dictionary, https://www.etymonline.com
4. ^ Klein, Ernest. A Comprehensive Etymological Dictionary of the English Language. 2 vols. Amsterdam: Elsevier, 1966–1967.
5. ^ a b c d e f g h Merriam-Webster Unabridged Dictionary (2024), online ed., Springfield, Mass.: Merriam-Webster
6. ^ a b c Shorter Oxford English Dictionary on Historical Principles (2002), 5th ed., ed. William R. Trumble and Angus Stevenson, Oxford: Oxford University Press
7. ^ Dictionary.com Unabridged (2016), based on the Random House Unabridged Dictionary, New York: Random House
8. ^ Johnson, Samuel (1755), A Dictionary of the English Language, London; 4th ed. 1773; Johnson's Dictionary Online, ed. Beth Rapp Young et al.
9. ^ a b c d Collins English Dictionary (2023), Glasgow: HarperCollins