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trimester

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Etymology and origin of the English word trimester

Confidence
Established
Formation
Borrowing
First attested
1821 S. Weston
Borrowed from
French trimestre
Ultimate origin
Latin trimēstris

Pronunciation

  • UK: /ˈtɹ(a)ɪ.mɛs.tə(ɹ)/, /tɹ(a)ɪˈmɛs.tə(ɹ)/[1]
  • US: /ˈt(ʃ)ɹaɪ.mɛs.təɹ/, /t(ʃ)ɹaɪˈmɛs.təɹ/[1]

Etymology

It is borrowed from French trimestre,[2][3][4][5][6] a noun recorded in French in Cotgrave's dictionary (1611),[2] a learned borrowing[4] from Latin trimēstris (“of three months”), also trimēnstris,[6][7] formed from tri- (“three”) and mēnsis (“month”),[6][4][7][5] which is related to moon.[5][3][4] Klein compares mēnstruus (“monthly”), and the Shorter Oxford semester.[7][8]

Earliest recorded meaning

A period of three months: 1821, in the title of a work by S. Weston.[2][4][5][3]

Semantic evolution

The specific sense in obstetrics, each of the three periods into which a human pregnancy is divided, is recorded from 1900.[3][2] In North America the word also names one of three terms of a school or university year.[8][5][9] The adjective trimestrial is older, from the 1690s.[3]

Timeline

  • 1821 – a period of three months.[2][3][4]
  • 1900 – each of the three periods of a human pregnancy.[3]

Meanings

Noun

  1. A period of three months, or about three months.[5][9][2]
  2. One of the three periods of about three months into which a human pregnancy is divided: She felt tired all through the first trimester.[8][2]
  3. (US, Canada) One of three terms into which some schools and universities divide the academic year.[5][9][8]

Word family

  • trimestral

References

  1. ^ a b Wiktionary, the free dictionary, https://en.wiktionary.org
  2. ^ a b c d e f g Oxford English Dictionary Online (accessed March 2026), Oxford: Oxford University Press
  3. ^ a b c d e f g Harper, Douglas. Online Etymology Dictionary, https://www.etymonline.com
  4. ^ a b c d e f Barnhart, Robert K. (1988), The Barnhart Dictionary of Etymology
  5. ^ a b c d e f g Merriam-Webster Unabridged Dictionary (2024), online ed., Springfield, Mass.: Merriam-Webster
  6. ^ a b c The American Heritage Dictionary of the English Language (online 2024), 5th ed., Boston: Houghton Mifflin Harcourt
  7. ^ a b c Klein, Ernest. A Comprehensive Etymological Dictionary of the English Language. 2 vols. Amsterdam: Elsevier, 1966–1967.
  8. ^ a b c d Shorter Oxford English Dictionary on Historical Principles (2002), 5th ed., ed. William R. Trumble and Angus Stevenson, Oxford: Oxford University Press
  9. ^ a b c Collins English Dictionary (2023), Glasgow: HarperCollins

Related etymologies

Cite this entry

“Trimester.” Etymologically, 2 Nov. 2026, etymologically.com/en/trimester. Accessed 2 Nov. 2026.

Last edited on . ·