probably

Etymology

It is formed from English probable + -ly,^[2][3][4][5] first spelled probabli, also probabili.^[6][3] The OED compares Middle French probablement, recorded from about 1370.^[2] The adjective is from Middle French probable (“having an appearance of truth”) and Latin probābilis (“that may be proved, credible, likely”),^[2][7] from probō (“to try, test; to show, demonstrate”),^[2][3] itself from probus (“worthy, good, upright”).^[3]

Earliest recorded meaning

In a way that the reason can accept; plausibly, credibly: about 1443, in Reginald Pecock's Reule of Crysten Religioun, where something has been probabili provid.^[2][6] Etymonline likewise dates it to the mid-15th century,^[3] and Merriam-Webster to the 15th,^[8] while Dictionary.com gives only 1525–35.^[5]

Semantic evolution

The word began as a term for the strength of an argument: a thing said probably was put in a way that commended itself to reason, though short of certainty.^[2][6] That older sense is now rare or archaic;^[4][8] Merriam-Webster illustrates it with Hobbes, who speaks of a problem so probably solved.^[8] From about 1600 the adverb also came to qualify a whole statement, "as far as one can tell, most likely",^[2][3][4] and the OED calls this the ordinary use today.^[2] Johnson (1755) glossed it simply as "likely; in likelihood", quoting L'Estrange's contrast between what may possibly and what will probably be done.^[9] It can also stand alone as a reply.^[10][4] American campus slang of the late 20th century used a bare, ironic probably to mean "probably not".^[11]

Timeline

• c. 1443 – in a way that is convincing to reason; plausibly.^[2][6]
• 1600 – as a sentence adverb, most likely, as far as one can tell.^[2] Etymonline dates this use to the 1610s.^[3]
• 1988 – ironic, in American campus slang: probably not.^[11]

Meanings

Adverb

1. Very likely; in all probability, so far as the evidence goes: We'll probably leave at noon.^[10][8][2]
2. As a reply on its own: I think that is likely: “Will they win?” “Probably.”^[10][4]
3. (American campus slang, ironic) Probably not.^[11]
4. (archaic) In a plausible or fairly convincing way.^[8][4]

Related words

• probable
• probability
• prove
• probe

References

1. ^ a b Wiktionary, the free dictionary, https://en.wiktionary.org
2. ^ a b c d e f g h i j k 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 Shorter Oxford English Dictionary on Historical Principles (2002), 5th ed., ed. William R. Trumble and Angus Stevenson, Oxford: Oxford University Press
5. ^ a b Dictionary.com Unabridged (2016), based on the Random House Unabridged Dictionary, New York: Random House
6. ^ a b c d 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)
7. ^ Hoad, T. F., ed. (1986), The Concise Oxford Dictionary of English Etymology, Oxford: Clarendon Press
8. ^ a b c d e Merriam-Webster Unabridged Dictionary (2024), online ed., Springfield, Mass.: Merriam-Webster
9. ^ Johnson, Samuel (1755), A Dictionary of the English Language, London; 4th ed. 1773; Johnson's Dictionary Online, ed. Beth Rapp Young et al.
10. ^ a b c Collins English Dictionary (2023), Glasgow: HarperCollins
11. ^ a b c Green, Jonathon (2010), Green's Dictionary of Slang, London: Chambers; digital ed. 2016–, https://greensdictofslang.com