sure

American  

[shoor, shur] / ʃʊər, ʃɜr /

adjective

• surer,
  comparative
• surest
  superlative

1. free from doubt as to the reliability, character, action, etc., of something.

   to be sure of one's data.

2. confident, as of something expected.

   sure of success.

3. convinced, fully persuaded, or positive.

   to be sure of a person's guilt.

4. assured or certain beyond question.

   a sure victory.

5. worthy of confidence; reliable; stable.

   a sure messenger.

6. unfailing; never disappointing expectations.

   a sure cure.

7. unerring; never missing, slipping, etc..

   a sure aim.

8. admitting of no doubt or question.

   sure proof.

9. destined; bound inevitably; certain.

   sure death.

10. Obsolete. secure; safe.

11. be sure, to take care (to be or do as specified); be certain.

    Be sure to close the windows.

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adverb

1. Informal. certainly; surely.

   It sure is cold out. Sure, I'll come.

idioms

1. for sure, as a certainty; surely.

   It's going to be a good day, for sure.

2. make sure, to be or become absolutely certain.

   I'm calling to make sure that you remember to come.

3. to be sure,

   1. without doubt; surely; certainly.

   2. admittedly.

      She sings well, to be sure, but she can't act.

4. sure enough, as might have been supposed; actually; certainly.

   Sure enough, the picnic was rained out.

sure British  

/ ʃɔː, ʃʊə /

adjective

1. (sometimes foll by of) free from hesitancy or uncertainty (with regard to a belief, conviction, etc)

   we are sure of the accuracy of the data

   I am sure that he is lying

2. (foll by of) having no doubt, as of the occurrence of a future state or event

   sure of success

3. always effective; unfailing

   a sure remedy

4. reliable in indication or accuracy

   a sure criterion

5. (of persons) worthy of trust or confidence

   a sure friend

6. not open to doubt

   sure proof

7. admitting of no vacillation or doubt

   he is very sure in his beliefs

8. bound to be or occur; inevitable

   victory is sure

9. (postpositive) bound inevitably (to be or do something); certain

   she is sure to be there tonight

10. physically secure or dependable

    a sure footing

11. obsolete free from exposure to harm or danger

12. (usually imperative or dependent imperative; takes a clause as object or an infinitive, sometimes with to replaced by and) to be careful or certain

    be sure and shut the door

    I told him to be sure to shut the door

13. without a doubt; surely

14. 1. (takes a clause as object) to make certain; ensure

    2. (foll by of) to establish or confirm power or possession (over)

15. informal as might have been confidently expected; definitely: often used as a sentence substitute

16. 1. without doubt; certainly

    2. it has to be acknowledged; admittedly

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adverb

1. informal (sentence substitute) willingly; yes

2. informal (sentence modifier) without question; certainly

sure More Idioms  

More idioms and phrases containing sure

• for certain (sure)
• make sure
• slow but sure
• to be sure

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Usage

What are other ways to say sure?

Someone who is sure of something is free from doubt about its reliability or character. How does sure compare to synonyms certain, confident, or positive? Learn more on Thesaurus.com. 

Commonly Confused

Both sure and surely are used as intensifying adverbs with the sense “undoubtedly, certainly.” In this use, sure is generally informal and occurs mainly in speech and written representations of speech: She sure dazzled the audience with her acceptance speech. It was sure hot enough in the auditorium. Surely is used in this sense in all varieties of speech and writing, even the most formal: The court ruled that the law was surely meant to apply to both profit-making and nonprofit organizations. See also quick, slow.

Other Word Forms

Derived Forms

• oversureness
  noun
• sureness
  noun
• unsureness
  noun
• oversure
  adjective
• unsure
  adjective
• oversurely
  adverb
• unsurely
  adverb

Inflected Forms

Adjectives

• surer
  comparative
• surest
  superlative

Etymology

Origin of sure

First recorded in 1300–50; Middle English sur(e), from Middle French sur, Old French seur, from Latin sēcūrus “carefree”; see secure

Explanation

Being sure has to do with being certain, convinced, trustworthy, or dependable. You can trust a sure thing. Besides being a synonym for yes, sure has to do with lots of kinds of dependability. If you have a sure eye, then you have good aim, maybe with shooting a basketball or throwing darts. If you're sure of yourself, you're confident. A sure thing or sure bet is something almost certain to happen. If you're 100% convinced of something, you're sure of it.

Example Sentences

See Examples For:

sure surer surest

A member of our team worked with a cross-functional partner on building a contract review tool that makes sure customer order forms exactly match with Salesforce.

From The Wall Street Journal ● Oct. 6, 2026

“My brother is the other caregiver, and he’s a lot more sensitive. I’m just like, oh, no, you need me. I’m going to make sure you’re OK,” she said.

From MarketWatch ● Oct. 6, 2026

Navigators also helped make sure patients completed important follow-up steps after appointments, including glucose tolerance testing and subsequent medical visits.

From Science Daily ● Oct. 6, 2026

"We need to make sure the building is safe for them to return," he said, adding people living there were likely to be face disruption for the rest of the day.

From BBC ● Oct. 6, 2026

I’m not sure how I expected her to react, but it wasn’t with a big smile.

From "Split the Sky" by Marie Arnold

The findings come as young people may see stock-market returns as providing a surer path to wealth than paychecks from a 9-to-5 job.

From MarketWatch ● Sep. 18, 2026

A surer bet, Lopez told listeners, is to buy a franchise like a McDonald’s or Taco Bell.

From The Wall Street Journal ● Feb. 10, 2026

If they even had a sliver of doubt before the Munich showdown against PSG they will be even surer now.

From BBC ● May 31, 2025

A perimeter defense on the western side of the Atlantic, he argued, would be surer and less likely to produce permanent American entanglement in European affairs.

From Salon ● Sep. 21, 2024

Nevertheless, he could not deny to himself that Eilonwy and Doli had proposed the surer plan.

From "The Black Cauldron" by Lloyd Alexander

The cable-television pioneer, who died in May at 87, demonstrated that the surest way to save an American icon was to give people a stake in it.

From The Wall Street Journal ● Oct. 2, 2026

Censorship, and worse, are the surest way to elevate an artist and their work.

From Los Angeles Times ● Sep. 19, 2026

If you were a songwriter in the 1930s, one of the surest routes to immortality was to have Fred Astaire introduce your work on screen.

From The Wall Street Journal ● Sep. 18, 2026

Once upon a time, platforming a trend on TV was the surest way to kill it.

From Salon ● Sep. 12, 2026

It was the surest sign of her desperation that she wanted to go to Babci’s cottage.

From "Not Nothing" by Gayle Forman

Related Words

• assured
• clear
• confident
• convinced
• positive