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Definitions

certain

[sur-tn] / ˈsɜr tn /
ADJECTIVE
confident
Synonyms
STRONGEST
convinced positive sure
WEAK
assertive assured believing calm cocksure questionless sanguine satisfied secure self-confident unconcerned undisturbed undoubtful undoubting unperturbed untroubled
Antonyms
STRONGEST
doubtful uncertain unsure
WEAK
doubting dubious faltering hesitant unconfident undecided
ADJECTIVE
undoubtable, valid
Synonyms
STRONGEST
absolute clear definite genuine positive real safe sure true undeniable
WEAK
ascertained authoritative conclusive confirmable demonstrable destined determined establishable evident firm fixed guaranteed having down pat in the bag incontrovertible indubitable infallible irrefutable known on ice plain predestined provable reliable salted away set sound supreme trustworthy unambiguous undoubted unequivocal unerring unmistakable verifiable
Antonyms
STRONGEST
counterfeit doubted doubtful false invalid uncertain unreal unsure vague
WEAK
questionable unpredictable unreliable
ADJECTIVE
fixed
Synonyms
STRONGEST
definite sure
WEAK
assured bound certified concluded decided determined ensured established guaranteed insured set settled stated stipulated warranted
Antonyms
STRONGEST
indefinite uncertain
WEAK
doubtful dubious questionable unfixed unpredictable unreliable
ADJECTIVE
referring to a specifically known amount
Synonyms
STRONGEST
individual numerous particular precise special specific specified various
WEAK
a couple a few defined divers express many marked one regular several singular some sundry upwards of
Antonyms
STRONGEST
common general imprecise indefinite inexact usual
WEAK
questionable uncertain undecided unpredictable unsure

Usage

What are other ways to say certain?

Certain, one of a handful of adjectives indicating full belief and trust that something is true, 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. Sure, the simplest and most general term, expresses mere absence of doubt. 

Example Sentences

Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.

The suit alleged the turbines emit pollution and hazardous chemicals that have been linked to increases in asthma, respiratory diseases, heart problems and certain cancers.

From The Wall Street Journal • Apr. 14, 2026

Credo may pay 3.21 million additional shares if certain financial milestones are reached.

From Barron's • Apr. 14, 2026

Just taking notes of how I want to incorporate certain things in my show or how I want to move, or the things I might need, it’s all been very rewarding.

From Los Angeles Times • Apr. 14, 2026

For instance, a self-employed taxpayer with a certain type of IRA can stretch the window for retirement contributions to Oct.

From MarketWatch • Apr. 14, 2026

She’d always tell us that we were only going to buy a certain number of tickets, and once they were gone, that was it.

From "Red Flags and Butterflies" by Sheryl Azzam

Vocabulary lists containing certain

The Real Deal: Synonyms for "True"

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List 1

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A Sure Thing: Synonyms for "Definite"

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