adverb
Etymology
Origin of certainly
Explanation
Use the adverb certainly when you’re sure about a particular action — absolutely, positively sure. If you love the new shoes you just bought, you may defend your purchase by saying they were certainly worth the money you paid. The word certainly emphasizes that you’re positive about something. When you hear thunder and look up at a gray sky, you might say it will certainly rain. If you’re on a diet, you could say that you will certainly avoid chocolate cake. Certainly can also be used to answer a question in the affirmative. If your boss asks to speak to you, you might answer, “Certainly.” It’s just a formal way of saying “yes.”
Vocabulary lists containing certainly
Florida's B.E.S.T. Common Suffixes: -ly
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"Alice's Adventures in Wonderland" by Lewis Carroll, Chapters 4–6
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Novel Study: Barrio Boy, Parts 1–3
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Example Sentences
Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.
“That certainly is not anything we’re taking for granted,” McVay said.
From Los Angeles Times ● Oct. 3, 2026
The point is that AI will almost certainly raise productivity and economic growth, but not necessarily in ways that translate directly into revenue, or the fat returns investors are counting on.
From The Wall Street Journal ● Oct. 2, 2026
"It's certainly going to be tricky for the court to thread the needle," said Sankar, between upholding the administration's position and giving the oil companies what they seek.
From Barron's ● Oct. 2, 2026
From the conversations BBC Sport have had with sources close to the first team, there is certainly a significant level of concern as to how they will be affected.
From BBC ● Oct. 2, 2026
It certainly may have allowed the sisters a bit of freedom to act unobserved.
From "American Spirits" by Barb Rosenstock
Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023
Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.
