Etymologically
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oculus

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Pronunciation

  • UK: /ˈɒk.jʊ.ləs/[1]
  • US: /ˈɑk.jə.ləs/[1]

Etymology

It is borrowed from Latin oculus (“eye”),[2][3][4][5][6] which in classical Latin could also mean a bud, the knob at the centre of the spiral scroll on a capital, and a marking like an eye;[2] the American Heritage Dictionary takes it through Medieval Latin.[7] The OED compares oculus, a small round church window, recorded in French from 1852.[2] The Latin word comes from Proto-Indo-European *okw- (“to see”),[3][7] and the OED gives as cognates Ancient Greek ὄσσεσθαι (óssesthai) and ὄψεσθαι (ópsesthai), Lithuanian akis, words in Sanskrit, Old Church Slavonic and Russian, and the Germanic base of eye.[2]

Earliest recorded meaning

A leaf bud, in botany: 1728, in E. Chambers's Cyclopaedia.[2] The Shorter Oxford finds the Latin word earlier in the plant name oculus Christi, wild clary, thought good for the eyes, from late Middle English to the mid 17th century.[6]

Semantic evolution

The botanical sense was rare and had died out by 1866.[2] From 1797, in the Encyclopaedia Britannica, oculus was used in zoology and botany for an eye, especially the compound eye of an insect, or an eyelike marking.[2][6] The architectural sense, a round or eyelike opening, such as a circular window or the opening at the top of a dome, is first recorded in 1848, in J. H. Parker's edition of Rickman's Styles of Architecture;[2][4] Etymonline dates the word to 1857.[3] Merriam-Webster also lists the central boss of a volute and an oeil-de-boeuf window, and the painted eye on the bow of a boat, as in ancient Egypt.[4] The Shorter Oxford records oculus mundi for hydrophane in the late 17th and 18th centuries.[6]

Timeline

  • 1728 – a leaf bud (obsolete by 1866).[2]
  • 1797 – an eye, especially the compound eye of an insect; an eyelike marking.[2]
  • 1848 – in architecture, a round opening or window.[2][4] Etymonline dates the word to 1857.[3]

Meanings

Noun

  1. In architecture, a round opening or window, especially one at the top of a dome: Light poured through the oculus onto the marble floor.[8][4][2][6]
  2. The central boss of a volute.[4][6]
  3. A painted eye on the bow of a boat.[4]
  4. (rare) In zoology and botany, an eye, especially a compound eye; a marking like an eye.[2][6]
  5. In botany, a leaf bud.[8][2]
  • ocular
  • oculist
  • ocellus
  • eye

Usage notes

The plural is oculi.[4][3][8]

References

  1. ^ a b Wiktionary, the free dictionary, https://en.wiktionary.org
  2. ^ a b c d e f g h i j k l m n Oxford English Dictionary Online (accessed March 2026), Oxford: Oxford University Press
  3. ^ a b c d e Harper, Douglas. Online Etymology Dictionary, https://www.etymonline.com
  4. ^ a b c d e f g h Merriam-Webster Unabridged Dictionary (2024), online ed., Springfield, Mass.: Merriam-Webster
  5. ^ Stevenson, Angus, ed. (2010), Oxford Dictionary of English, 3rd ed., Oxford: Oxford University Press
  6. ^ a b c d e f g Shorter Oxford English Dictionary on Historical Principles (2002), 5th ed., ed. William R. Trumble and Angus Stevenson, Oxford: Oxford University Press
  7. ^ a b The American Heritage Dictionary of the English Language (online 2024), 5th ed., Boston: Houghton Mifflin Harcourt
  8. ^ a b c Collins English Dictionary (2023), Glasgow: HarperCollins