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

There will almost certainly be more of these moments this week, as some of the biggest names in AI take to the stage at the AI Impact Summit in India. —Yeo Boon Ping, CNBC, 16 Feb. 2026

Sweating the outcome, certainly – and actually, literally sweating. —Mirjam Swanson, Oc Register, 16 Feb. 2026

That would certainly be something that would be worth pursuing. —New Atlas, 15 Feb. 2026

Eric Warren, Chevy’s VP of global motorsports competition, certainly thinks the new postseason format will change things. —Alex Zietlow, Charlotte Observer, 15 Feb. 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