certainly

Etymology

It is formed from English certain + -ly in Middle English.^{[2][3][4][5][6]} Certain is from Old French certain (“reliable, sure”), from Vulgar Latin *certānus, an extended form of Latin certus (“determined, fixed, sure”),^[2][7][8][9] originally a past participle of cernō (“to sift, separate, decide”).^[7][8][9]

Earliest recorded meaning

Without doubt or question, assuredly: about 1300, according to Etymonline.^[2] The OED's earliest quotation for "without doubt" is from William of Palerne, before 1375, and those for "with certainty", "without fail" and "surely" are from the Cursor Mundi, before 1400.^[3] Dictionary.com dates the word to 1250–1300.^[6]

Semantic evolution

From about 1460, in Fortescue, the adverb could also mean "precisely, exactly", a sense that had died out by the early 17th century.^[3][4] Shakespeare used it for "fixedly, unalterably".^[3] The sense "without doubt" is often used in replies, as an emphatic "yes";^[3][4] Collins classes this use as a sentence substitute, "by all means".^[10] Johnson (1755) defined it as "indubitably; without question; without doubt".^[11] In East Yorkshire dialect it was also an interrogative protest, "surely?".^[12]

Timeline

• c. 1300 – without doubt, assuredly.^[2] The OED's first quotation for this sense is from before 1375.^[3]
• before 1400 – with certainty; without fail; with assurance, in the Cursor Mundi.^[3]
• c. 1460 – precisely, exactly (obsolete by the early 17th century).^[3][4]
• before 1616 – fixedly, unalterably, in Shakespeare.^[3]

Meanings

Adverb

1. Without doubt; undoubtedly, surely: He certainly knows how to cook.^[10][5][3]
2. With certainty; in a way that can be relied on; without fail.^[5][3]
3. In replies: yes, by all means: “Could you pass the salt?” “Certainly.”^[10][3]
4. (obsolete) Precisely, exactly.^[3][4]

Related words

• certain
• certainty
• certify
• ascertain
• discern

References

1. ^ a b Wiktionary, the free dictionary, https://en.wiktionary.org
2. ^ a b c d Harper, Douglas. Online Etymology Dictionary, https://www.etymonline.com
3. ^ a b c d e f g h i j k l m Oxford English Dictionary Online (accessed March 2026), Oxford: Oxford University Press
4. ^ a b c d e Shorter Oxford English Dictionary on Historical Principles (2002), 5th ed., ed. William R. Trumble and Angus Stevenson, Oxford: Oxford University Press
5. ^ a b c Merriam-Webster Unabridged Dictionary (2024), online ed., Springfield, Mass.: Merriam-Webster
6. ^ a b Dictionary.com Unabridged (2016), based on the Random House Unabridged Dictionary, New York: Random House
7. ^ a b Barnhart, Robert K. (1988), The Barnhart Dictionary of Etymology
8. ^ a b Hoad, T. F., ed. (1986), The Concise Oxford Dictionary of English Etymology, Oxford: Clarendon Press
9. ^ a b Ayto, John (2005), Word Origins: The Secret Histories of English Words from A to Z, 2nd ed., London: A & C Black
10. ^ a b c Collins English Dictionary (2023), Glasgow: HarperCollins
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. ^ Wright, Joseph, ed. (1898–1905), The English Dialect Dictionary, 6 vols., Oxford: Henry Frowde; via EDD Online 4.0, University of Innsbruck (CC BY 4.0)