Synonyms for Certain:

adj.

absolute (adjective)
unconditional, unequivocal, complete, consummate, utter, indubitable, unrestricted, sure, positive, absolute, unmitigated, definite, conclusive, supreme, undeniable, unqualified, categorical, perfect.
accepted (adjective)
undisputed.
affirmative (adjective)
categorical, predicative, assertive, definite, positive, sure, insistent, affirmative, declarative.
aggressive (adjective)
assertive.
beyond doubt (adjective)
indisputable.
beyond question (adjective)
irrefutable.
categorical (adjective)
outright, absolute, indubitable, typical, definite, categorical, denominational, sure, unequivocal, undeniable, flat, unconditional, unqualified.
certain (adjective)
unmistakable, patent, set, steadfast, confident, incontestable, incontrovertible, unequivocal, irrefutable, positive, decisive, indisputable, doubtless, convinced, indubitable, definite, absolute, trusting, assured, decided, sure, Irrefragable, veritable, undoubted, clear, undeniable, unquestionable.
confident (adjective)
sure, believing, calm, unperturbed, Questionless, self-confident, secure, untroubled, undisturbed, unconcerned, satisfied, assured, assertive, undoubting, positive, convinced.
content (adjective)
satisfied.
fixed (adjective)
decided, concluded, settled.
perfect (adjective)
perfect.
reliable (adjective)
loyal, devoted, trustworthy, conscientious, faithful, trusty, reliable, dependable.
sure-fire (adjective)
sure-fire.
true (adjective)
honest, true, authentic, veracious, axiomatic, definite, proven, factual, right, gospel, absolute.
trusting (adjective)
believing.
unavoidable (adjective)
inescapable.
undisputed (adjective)
undoubted.
unerring (adjective)
unerring.

n.

objective, definitely, sound, realistic. every, dozen, determined, mine, Its, My, double, an, determiner. good, have confidence, probably, make certain, feel sure, have no doubt, know, be confident, possibly, likely, expected, probable. firm, change, fixed. inevitable, inescapable, unavoidable. inarguable, hard, undisputable, unassailable. sure-fire, unerring, infallible, unfailing, secure. undoubting. certain (noun)
particular, definite, inevitable, clear, inescapable, indisputable, specific, fixed, special, convinced, decided, undeniable, absolute, conclusive, undoubted, evident, assured, positive, confident, unquestionable, some, incontrovertible, irrefutable, unavoidable, determined, express, precise, plain, destined, individual, indubitable, sure, true, settled.
confident (noun)
calm, unwavering, undisturbed, undoubting, untroubled, Questionless, satisfied, unperturbed, self-confident, secure, believing, unconcerned.
dependable (noun)
safe.
fixed (noun)
settled, concluded.
sure (noun)
determined, destined, inevitable.

Other synonyms:

secure. double. firm. open. hard. good. fated
inevitable.
inescapable
unavoidable.
sure
unfailing.
unchallenged
undisputed.
unerring
infallible.
without doubt
Questionless.

Usage examples for certain

  1. This fact is certain – The Memoirs of Louis XIV., Volume 10 And His Court and of The Regency by Duc de Saint-Simon
  2. No, replied the man, I will not, that is certain – New-Arabian-Nights by Stevenson, Robert Louis