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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.

They had requested lawmakers approve a temporary holiday from certain taxes on airline tickets.

From The Wall Street Journal • Apr. 27, 2026

During the phone conversation, the call handler tried to tell the councillor about "disruptive sounds" on the line and asked her to repeat certain information.

From BBC • Apr. 26, 2026

In the 1950s, the Court under Warren began to tighten the rules for denaturalization on the grounds that using it as punishment for certain acts was cruel and inhuman.

From Salon • Apr. 26, 2026

You can choose to block individual apps; whole categories of app, like social media or games; or even certain URLs.

From Slate • Apr. 26, 2026

“I shouldn’t have reacted the way I did, especially since I was fairly certain it wasn’t your fault.”

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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