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sure

[shoo r, shur]
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adjective, sur·er, sur·est.
  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.
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. sure enough, Informal. as might have been supposed; actually; certainly: Sure enough, the picnic was rained out.
  4. 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 formssure·ness, nouno·ver·sure, adjectiveo·ver·sure·ly, adverbo·ver·sure·ness, nounun·sure, adjectiveun·sure·ly, adverbun·sure·ness, noun

Synonyms

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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.
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018
British Dictionary definitions for to be sure

sure

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 eventsure of success
  3. always effective; unfailinga sure remedy
  4. reliable in indication or accuracya sure criterion
  5. (of persons) worthy of trust or confidencea sure friend
  6. not open to doubtsure proof
  7. admitting of no vacillation or doubthe is very sure in his beliefs
  8. bound to be or occur; inevitablevictory is sure
  9. (postpositive) bound inevitably (to be or do something); certainshe is sure to be there tonight
  10. physically secure or dependablea sure footing
  11. obsolete free from exposure to harm or danger
  12. 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 certainbe sure and shut the door; I told him to be sure to shut the door
  13. for sure without a doubt; surely
  14. make sure
    1. (takes a clause as object)to make certain; ensure
    2. (foll by of)to establish or confirm power or possession (over)
  15. sure enough informal as might have been confidently expected; definitely: often used as a sentence substitute
  16. to be sure
    1. without doubt; certainly
    2. it has to be acknowledged; admittedly
adverb
  1. (sentence substitute) informal willingly; yes
  2. (sentence modifier) informal, mainly US and Canadian without question; certainly
Derived Formssureness, noun

Word Origin

C14: from Old French seur, from Latin sēcūrus secure
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

Word Origin and History for to be sure

sure

adj.

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

Idioms and Phrases with to be sure

to be sure

Undoubtedly, certainly, of course, as in The coat is expensive, to be sure, but it's bound to last longer than a cheap one. This idiom was first recorded in 1657.

sure

In addition to the idioms beginning with sure

also see:

The American Heritage® Idioms Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.