• synonyms


See more synonyms for certain on Thesaurus.com
  1. free from doubt or reservation; confident; sure: I am certain he will come.
  2. destined; sure to happen (usually followed by an infinitive): He is certain to be there.
  3. inevitable; bound to come: They realized then that war was certain.
  4. established as true or sure; unquestionable; indisputable: It is certain that he tried.
  5. fixed; agreed upon; settled: on a certain day; for a certain amount.
  6. definite or particular, but not named or specified: A certain person phoned. He had a certain charm.
  7. that may be depended on; trustworthy; unfailing; reliable: His aim was certain.
  8. some though not much: a certain reluctance.
  9. Obsolete. steadfast.
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  1. certain ones: Certain of the members declined the invitation.
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  1. for certain, without a doubt; surely: I know for certain that I have seen that face before.
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Origin of certain

1250–1300; Middle English < Old French < Vulgar Latin *certānus, equivalent to Latin cert(us) sure, settled (cer- base of cernere to decide, + -tus past participle suffix) + -ānus -an


See more synonyms for on Thesaurus.com
1. convinced, satisfied. See sure. 4. indubitable, incontestable, irrefutable, incontrovertible, obvious, plain, clear. 5. determined.
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

British Dictionary definitions for for certain


  1. (postpositive) positive and confident about the truth of something; convincedI am certain that he wrote a book
  2. (usually postpositive) definitely knownit is certain that they were on the bus
  3. (usually postpositive) sure; bound; destinedhe was certain to fail
  4. decided or settled upon; fixedthe date is already certain for the invasion
  5. unfailing; reliablehis judgment is certain
  6. moderate or minimumto a certain extent
  7. make certain of to ensure (that one will get something); confirm
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  1. for certain definitely; without a doubthe will win for certain
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    1. known but not specified or namedcertain people may doubt this
    2. (as pronoun; functioning as plural)certain of the members have not paid their subscriptions
  1. named but not knownhe had written to a certain Mrs Smith
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Word Origin

C13: from Old French, from Latin certus sure, fixed, from cernere to discern, decide
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 for certain



c.1300, "determined, fixed," from Old French certain "reliable, sure, assured" (12c.), from Vulgar Latin *certanus, from Latin certus "sure, fixed, settled, determined" (also source of Italian certo, Spanish cierto), originally a variant past participle of cernere "to distinguish, decide," literally "to sift, separate" (see crisis).

Of persons, "full of confidence in one's knowledge or judgment," from mid-14c. Euphemistic use (of a certain age, etc.) attested from mid-18c. Certainer, certainest were common to c.1750, but have fallen from proper use for some reason. Expression for certain "assuredly" is attested by early 14c.

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Online Etymology Dictionary, © 2010 Douglas Harper

Idioms and Phrases with for certain

for certain

Also, for sure. Without doubt. For example, I can't tell for certain if this is the right color, or I know for sure that she has a new car. The first term dates from the early 1300s. The variant, dating from the late 1500s, is also used colloquially to express agreement or assert the truth of a statement, as in Mary is really bossy.—That's for sure, or Are you coming to the party?—For sure I am.

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see for certain.

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