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

Shareef Elaydi certainly falls into that top-end category. —Glenn Reeves, Mercury News, 10 May 2026

Policymakers certainly ought to focus on this. —Editorial, Boston Herald, 10 May 2026

His most fulfilling moment was when the fourth calf was born in the wild last year, an indication that the bongos are thriving in their native habitat and that their population will certainly increase. —ABC News, 9 May 2026

But yeah, that was certainly my happy place this past week. —Lexi Lane, PEOPLE, 9 May 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