sure

UK: /ˈʃʊə^r/, /ˈʃɔː^r/ US: /ʃʊr/ ,(shŏŏr, shûr)

Inflections of 'sure' (adj):

surer

adj comparative

surest

adj superlative

WordReference Random House Learner's Dictionary of American English © 2025

sure /ʃʊr/   adj., sur•er, sur•est, adv. 
adj. 

1. (of a person) free from doubt as to the reliability, character, action, etc., of something: [be + ~ (+ of/about)]
   Are you sure? —Well, I'm pretty sure. She was very sure of her facts.
   [be + ~ + (that) clause]
   was sure (that) she had told him.
2. confident, as of something expected: [be/feel + ~ + of]
   They felt sure of success.
   [be + ~ + (that) clause]
   He was sure (that) he wouldn't fail again.
3. convinced, fully persuaded, or positive:
   [be + ~] to be sure of a person's honesty.
4. assured or certain beyond question:
   [before a noun] a sure victory.
5. never missing or disappointing;
   unfailing:
   [before a noun] This investment is a sure thing.
6. allowing for no doubt or question:
   [before a noun] Those high clouds are a sure sign of snow.
7. destined;
   certain:
   [be + ~ + to + verb] It is sure to happen.

adv. 

8. Informal Terms certainly;
   surely:
   She sure acts funny sometimes.

Idioms

9. Idioms be or make sure, to take care (to be or do as specified): [be + ~ + to + verb]
   Be sure to set your alarm clock.
   [make + ~ + (that) clause]
   Could you make sure (that) everything is OK with our checking account?
10. Idioms for sure, without a doubt;
    surely;
    for certain:
    We'd like to know for sure if you're on our side.
11. Idioms, Informal Terms sure enough, [Informal.] as might have been expected;
    certainly:
    As soon as I brought the car to the service station, sure enough the weird sound went away.

sure•ness, n. [uncountable]

WordReference Random House Unabridged Dictionary of American English © 2025

sure  (shŏŏr, shûr), adj., sur•er, sur•est, adv. 
adj. 

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. [Obs.] secure;
    safe.
11. be sure, to take care (to be or do as specified);
    be certain:
    Be sure to close the windows.
12. for sure, as a certainty;
    surely:
    It's going to be a good day, for sure.
13. make sure, to be or become absolutely certain:
    I'm calling to make sure that you remember to come.
14. Informal Terms sure enough, as might have been supposed;
    actually;
    certainly:
    Sure enough, the picnic was rained out.
15. to be sure:
    • without doubt;
      surely;
      certainly.
    • admittedly:
      She sings well, to be sure, but she can't act.

adv. 

16. Informal Terms certainly;
    surely:
    It sure is cold out. Sure, I'll come.

• Latin sēcūrus secure
• Middle French sur, Old French seur
• Middle English sur(e) 1300–50

sure′ness, n. 
Synonyms

• 1. Sure, certain, confident, positive indicate full belief and trust that something is true.
  Sure, certain, and positive are often used interchangeably.
  Sure, the simplest and most general, expresses mere absence of doubt.
  Certain suggests that there are definite reasons that have freed one from doubt.
  Confident emphasizes the strength of the belief or the certainty of expectation felt.
  Positive implies emphatic certainty, which may even become overconfidence or dogmatism.

Usage

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. 

Collins Concise English Dictionary © HarperCollins Publishers::

sure / ʃʊə ʃɔː/ adjective

1. (sometimes followed 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. (followed 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. be sure ⇒ (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
12. for sure ⇒ without a doubt; surely
13. make sure ⇒ (takes a clause as object) to make certain; ensure
14. (followed by of) to establish or confirm power or possession (over)
15. sure enough ⇒ as might have been confidently expected; definitely: often used as a sentence substitute
16. to be sure ⇒ without doubt; certainly
17. it has to be acknowledged; admittedly

adverb

1. (sentence substitute) willingly; yes
2. (sentence modifier) without question; certainly

Etymology: 14th Century: from Old French seur, from Latin sēcūrus secure

ˈsureness noun