certainly

adverb

cer·​tain·​ly ˈsər-tᵊn-lē 

1

: in a manner that is certain : with certainty

2

: it is certain that : assuredly

Synonyms of certainly

• definitely
• surely
• sure
• clearly
• probably
• really

Examples of certainly in a Sentence

It will certainly rain tomorrow.

This year's festival was certainly much better than last year's.

I'm certainly going to try.

The new version is most certainly easier to use.

The snake that bit her was almost certainly poisonous.

Recent Examples on the Web

My sisters certainly haven’t lost me to Hugh. —David Sedaris, New Yorker, 13 Apr. 2026

If there's a better version of Madison Taylor, that would certainly be scary for any of the Wildcats opponents the rest of the way. —Matt Zahn, CBS News, 13 Apr. 2026

Apollo’s manly, all-business moon crews of the 1960s and 1970s certainly did not do group hugs. —Marcia Dunn, Fortune, 12 Apr. 2026

But over the years, their festival fashions have most certainly evolved. —Anna Cafolla, Vogue, 12 Apr. 2026

Word History

First Known Use

14th century, in the meaning defined at sense 1

Phrases Containing certainly

• certainly not

Rhymes for certainly

• uncertainly

Kids Definition

certainly

adverb

cer·​tain·​ly ˈsərt-ᵊn-lē 

1

: in a manner that is certain : for certain

the only event of which anything is certainly known

2

: without doubt : surely

certainly you can do it