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

Ball certainly didn’t have any issue getting into the action, posting a team-best 11 first-quarter points on the strength of making his first three attempts and banking in a running 3-pointer off the glass at the buzzer, signaling the conclusion of the game’s initial 12 minutes. —Roderick Boone, Charlotte Observer, 9 Jan. 2026

And God Created Woman is certainly no great shakes as a work of cinema. —Peter Tonguette, The Washington Examiner, 9 Jan. 2026

Anyone who has paid attention certainly knows better. —Sal Rodriguez, Oc Register, 9 Jan. 2026

While the outcome was certainly tragic, I am heartened by the massive community turnout of residents, employees, police officers, firefighters and neighboring law enforcement agencies who stepped up to help with the search. —Jack Springgate, CBS News, 8 Jan. 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