Etymologically
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improbable

This is the current revision of this entry, as edited by bogdan on 31 October 2026 at 23:36. This address is a permanent link to this version.
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Pronunciation

  • UK: /ɪmˈpɹɒbəbl̩/[1]
  • US: /ɪmˈpɹɑbəbl̩/[1]

Etymology

The OED takes it as borrowed from Latin improbābilis, formed from in- (“not”) and probābilis (“probable, likely”), and compares improbable, first recorded in Cotgrave in 1611.[2][3] The Shorter Oxford, the Oxford Dictionary of English and Merriam-Webster allow French or Latin as the source.[4][5][6] Barnhart and Etymonline take it as probably formed from English im- + probable, perhaps after Italian improbabile, or else from Latin.[7][8] The Latin adjective meant "hard to prove" or "not deserving of approval",[4][3] and probābilis comes from probō (“to test, prove”), the source of prove.[3][9]

Earliest recorded meaning

Not likely to be true or to happen: 1598, in Florio's Italian–English dictionary A Worlde of Wordes.[2][7] Etymonline and Dictionary.com also date the word to the 1590s.[8][10]

Semantic evolution

The sense has stayed close to "unlikely" since 1598.[2] By 1617 it qualified a clause, as in "it is improbable that…",[2] and by 1659 it could also describe a person or thing unlikely to suit, or one that does not look the part.[2] Johnson (1755) defined it as "unlikely; incredible".[11] Merriam-Webster and the Shorter Oxford also record it for things that are unlikely yet real or true.[6][4]

Timeline

  • 1598 – not likely to be true or to happen, in Florio.[2][7]
  • 1617 – qualifying a clause, it is improbable that.[2]
  • 1659 – unlikely to suit, or not looking the part.[2]

Meanings

Adjective

  1. Not probable; unlikely to be true or to happen; hard to believe: It seems improbable that the train will arrive on time.[12][6][2]
  2. Unlikely, yet real or true: The underdogs staged an improbable comeback.[6][4]

Word family

  • improbableness
  • improbably
  • improbability
  • superimprobable

References

  1. ^ a b Wiktionary, the free dictionary, https://en.wiktionary.org
  2. ^ a b c d e f g h i Oxford English Dictionary Online (accessed March 2026), Oxford: Oxford University Press
  3. ^ a b c Klein, Ernest. A Comprehensive Etymological Dictionary of the English Language. 2 vols. Amsterdam: Elsevier, 1966–1967.
  4. ^ 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
  5. ^ Stevenson, Angus, ed. (2010), Oxford Dictionary of English, 3rd ed., Oxford: Oxford University Press
  6. ^ a b c d Merriam-Webster Unabridged Dictionary (2024), online ed., Springfield, Mass.: Merriam-Webster
  7. ^ a b c Barnhart, Robert K. (1988), The Barnhart Dictionary of Etymology
  8. ^ a b Harper, Douglas. Online Etymology Dictionary, https://www.etymonline.com
  9. ^ Partridge, Eric (1966), Origins: A Short Etymological Dictionary of Modern English, 4th ed., London: Routledge & Kegan Paul
  10. ^ Dictionary.com Unabridged (2016), based on the Random House Unabridged Dictionary, New York: Random House
  11. ^ Johnson, Samuel (1755), A Dictionary of the English Language, London; 4th ed. 1773; Johnson's Dictionary Online, ed. Beth Rapp Young et al.
  12. ^ Collins English Dictionary (2023), Glasgow: HarperCollins