acuity

Etymology

It is inherited from Middle English acuite (“sharpness, acridity”),^[2][3] partly borrowed from Middle French acuité (“sharpness”)^[4][3][5][6] and partly borrowed from Medieval Latin acuitās (“sharpness”),^[4][5][7][6] from Latin acuō (“to sharpen”) and the suffix -itās.^[4][3][5] The OED records the French word from before 1320 and the post-classical Latin one, for sharpness of intellect, from the 6th century.^[4] The Latin verb is related to acus (“needle”) and acūtus (“sharp”), the source of acute,^[5][8][9] and Etymonline traces it to Proto-Indo-European *ak- (“to be sharp, rise to a point, pierce”).^[5]

Earliest recorded meaning

Sharpness, acridity or corrosiveness of blood, an ulcer or a medicine: before 1390, in Daniel's Herbal.^[2] The OED's first record, of the cutting or corrosive power of a substance, is from before 1400, in a translation of Lanfranc's surgery.^[4] Etymonline dates the word to the early 15th century,^[5] and Barnhart to probably before 1425.^[7]

Semantic evolution

The word began in medicine and herbals for the biting quality of a substance,^[2][4] and the literal sharpness of a knife or point followed in 1598; the first sense was last recorded in 1714 and the second in 1699.^[4] The figurative sense, sharpness of thought or understanding, is recorded from about 1549,^[4][3] and the sense now usual, keenness of perception and especially of sight, from 1866, in a medical journal.^[4] In medicine the word has also meant, since 1839, the degree to which a disease is acute.^[4]

Timeline

• before 1390 – sharpness or corrosiveness of a substance (now obsolete).^[2][4]
• c. 1549 – sharpness of thought or understanding.^[4][3]
• 1598 – sharpness of a knife or point (obsolete by 1699).^[4]
• 1839 – in medicine, the acuteness of a disease.^[4]
• 1866 – keenness of perception, especially of vision.^[4]

Meanings

Noun

1. Sharpness or keenness of thought or understanding; perceptiveness: Her acuity in negotiations surprised her rivals.^[10][3][4]
2. Keenness of a sense, especially the eye's capacity to see fine detail (visual acuity).^[10][3][4]
3. (medicine) The degree to which a disease is acute.^[4]
4. (obsolete, before 1400–1714) The cutting or corrosive quality of a substance.^[4][2]

Word family

• hyperacuity
• visual acuity

Related words

• acute
• acutance
• acrid
• acuteness

References

1. ^ Wiktionary, the free dictionary, https://en.wiktionary.org
2. ^ a b c d e Kurath, Hans; Kuhn, Sherman M.; Lewis, Robert E., eds. (1952–2001), Middle English Dictionary, Ann Arbor: University of Michigan Press; online edition ed. Frances McSparran et al. (2000–2018)
3. ^ a b c d e f g Merriam-Webster Unabridged Dictionary (2024), online ed., Springfield, Mass.: Merriam-Webster
4. ^ a b c d e f g h i j k l m n o p q r s Oxford English Dictionary Online (accessed March 2026), Oxford: Oxford University Press
5. ^ a b c d e f Harper, Douglas. Online Etymology Dictionary, https://www.etymonline.com
6. ^ a b Hoad, T. F., ed. (1986), The Concise Oxford Dictionary of English Etymology, Oxford: Clarendon Press
7. ^ a b Barnhart, Robert K. (1988), The Barnhart Dictionary of Etymology
8. ^ Klein, Ernest. A Comprehensive Etymological Dictionary of the English Language. 2 vols. Amsterdam: Elsevier, 1966–1967.
9. ^ The American Heritage Dictionary of the English Language (online 2024), 5th ed., Boston: Houghton Mifflin Harcourt
10. ^ a b Collins English Dictionary (2023), Glasgow: HarperCollins