sure
Americanadjective
-
surer,
comparative
-
surest
superlative
-
free from doubt as to the reliability, character, action, etc., of something.
to be sure of one's data.
-
confident, as of something expected.
sure of success.
-
convinced, fully persuaded, or positive.
to be sure of a person's guilt.
-
assured or certain beyond question.
a sure victory.
-
worthy of confidence; reliable; stable.
a sure messenger.
-
unfailing; never disappointing expectations.
a sure cure.
-
unerring; never missing, slipping, etc..
a sure aim.
-
admitting of no doubt or question.
sure proof.
-
destined; bound inevitably; certain.
sure death.
-
Obsolete. secure; safe.
-
be sure, to take care (to be or do as specified); be certain.
Be sure to close the windows.
adverb
idioms
-
for sure, as a certainty; surely.
It's going to be a good day, for sure.
-
make sure, to be or become absolutely certain.
I'm calling to make sure that you remember to come.
-
to be sure,
-
without doubt; surely; certainly.
-
admittedly.
She sings well, to be sure, but she can't act.
-
-
sure enough, as might have been supposed; actually; certainly.
Sure enough, the picnic was rained out.
adjective
-
(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
-
(foll by of) having no doubt, as of the occurrence of a future state or event
sure of success
-
always effective; unfailing
a sure remedy
-
reliable in indication or accuracy
a sure criterion
-
(of persons) worthy of trust or confidence
a sure friend
-
not open to doubt
sure proof
-
admitting of no vacillation or doubt
he is very sure in his beliefs
-
bound to be or occur; inevitable
victory is sure
-
(postpositive) bound inevitably (to be or do something); certain
she is sure to be there tonight
-
physically secure or dependable
a sure footing
-
obsolete free from exposure to harm or danger
-
(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
-
without a doubt; surely
-
-
(takes a clause as object) to make certain; ensure
-
(foll by of) to establish or confirm power or possession (over)
-
-
informal as might have been confidently expected; definitely: often used as a sentence substitute
-
-
without doubt; certainly
-
it has to be acknowledged; admittedly
-
adverb
-
informal (sentence substitute) willingly; yes
-
informal (sentence modifier) without question; certainly
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
-
oversurenessnoun
-
surenessnoun
-
unsurenessnoun
-
oversureadjective
-
unsureadjective
-
oversurelyadverb
-
unsurelyadverb
Inflected Forms
Adjectives
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
Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.
See Examples For:
And the country sure does look splendid through the windows of brand new cars, upscale hotels and expensive ski resorts.
From Los Angeles Times ● Aug. 21, 2026
"You wouldn't put holes in your flask if you wanted to keep the ice in. You'd close the cap and make sure it is firmly twisted on. It's the same in this house."
From BBC ● Aug. 21, 2026
If you’re ever asked to sign a non-compete agreement again, be sure you’re totally comfortable with its parameters.
From MarketWatch ● Aug. 21, 2026
“We’re not quite sure what the rules of the sport are, so we’re a little lost,” said Hughes, 57, who was hosting her college pals at her nearby summer home.
From The Wall Street Journal ● Aug. 21, 2026
All day, Phineas must keep an eye on his drillers to make sure they stay ahead.
From "Phineas Gage" by John Fleischman
Round after round, the Hurricanes have knocked off teams that seemed surer bets to make the championship.
From The Wall Street Journal ● Jan. 9, 2026
A surer indicator is to observe what’s popular in the current marketplace.
From Salon ● Jun. 1, 2025
The closer the algorithm puts a specific chart toward the tip of an arm, the surer it is of its decision, while those placed closer to the central body are less certain.
From Science Daily ● May 29, 2024
But I’m now surer of the impression I had of him after we first talked.
From Los Angeles Times ● Feb. 27, 2024
Kimberly snuggles closer, and I hold her against me, surer than ever that it was a bad mistake to draw her in like this.
From "How It Went Down" by Kekla Magoon
A. Cooking produce to 158 degrees Fahrenheit is the surest way to eliminate the risk of contamination as it helps to kill most bacteria.
From The Wall Street Journal ● Jul. 31, 2026
Cooking produce to 158 degrees Fahrenheit is the surest way to eliminate risk of contamination, experts say.
From The Wall Street Journal ● Jul. 23, 2026
Refusing to be drawn into operational details, Miliband reiterated that "ending the conflict is the best and surest way to get the strait reopened".
From BBC ● Mar. 17, 2026
The surest sign of market dislocation is when banks start quantifying their exposure to a given issue.
From MarketWatch ● Feb. 24, 2026
Confronting Chas Becker with the truth was the surest way to get him to think I was lying.
From "Winger" by Andrew Smith
Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023
Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.
