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[shoo r, shur] /ʃʊər, ʃɜr/
adjective, surer, surest.
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.
Informal. certainly; surely:
It sure is cold out. Sure, I'll come.
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.
sure enough, Informal. as might have been supposed; actually; certainly:
Sure enough, the picnic was rained out.
to be sure,
  1. without doubt; surely; certainly.
  2. admittedly:
    She sings well, to be sure, but she can't act.
Origin of sure
1300-50; Middle English sur(e) < Middle French sur, Old French seur < Latin sēcūrus secure
Related forms
sureness, noun
oversure, adjective
oversurely, adverb
oversureness, noun
unsure, adjective
unsurely, adverb
unsureness, noun
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 note
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. Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2018.
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Examples from the Web for sure
Contemporary Examples
Historical Examples
  • Without reasons I was sure of, you know, so there could be no chance of any mistake.

    The Spenders Harry Leon Wilson
  • But if she had any such thing I'm sure it was ended, and she'd have jumped at this chance a year ago.

    The Spenders Harry Leon Wilson
  • In you I was sure of a mind strong enough to break the fetters of habit.

    Philothea Lydia Maria Child
  • "I just wanted to be sure you were all right," said Percival, greatly relieved.

    The Spenders Harry Leon Wilson
  • "I am sure some of the old man's money is here," he said to himself.

    Brave and Bold Horatio Alger
British Dictionary definitions for sure


/ʃʊə; ʃɔː/
(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) be sure, to be careful or certain: be sure and shut the door, I told him to be sure to shut the door
for sure, without a doubt; surely
make sure
  1. (takes a clause as object) to make certain; ensure
  2. (foll by of) to establish or confirm power or possession (over)
(informal) sure enough, as might have been confidently expected; definitely: often used as a sentence substitute
to be sure
  1. without doubt; certainly
  2. it has to be acknowledged; admittedly
(sentence substitute) (informal) willingly; yes
(sentence modifier) (informal, mainly US & Canadian) without question; certainly
Derived Forms
sureness, noun
Word Origin
C14: from Old French seur, from Latin sēcūrussecure
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition
© William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins
Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
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Word Origin and History for sure

c.1300, "safe, secure," later "mentally certain" (mid-15c.), from Old French sur, seur "safe, secure," from Latin securus "free from care, untroubled, heedless, safe" (see secure (adj.)). Pronunciation development followed that of sugar. As an affirmative meaning "yes, certainly" it dates from 1803, from Middle English meanings "firmly established; having no doubt," and phrases like to be sure (1650s), sure enough (1540s), and for sure (1580s). The use as a qualifier meaning "assuredly" goes back to early 15c. Sure-footed is from 1630s; sure thing dates from 1836. In 16c.-17c., Suresby was an appellation for a person to be depended upon.

Online Etymology Dictionary, © 2010 Douglas Harper
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Slang definitions & phrases for sure



Yes; certainly: Sure, I'll support you (1842+)

Related Terms


The Dictionary of American Slang, Fourth Edition by Barbara Ann Kipfer, PhD. and Robert L. Chapman, Ph.D.
Copyright (C) 2007 by HarperCollins Publishers.
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Idioms and Phrases with sure
The American Heritage® Idioms Dictionary
Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.
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