most certain

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 indefinite uncertain unsure

WEAK

doubting dubious faltering hesitant questionable unconfident undecided unfixed unpredictable unreliable

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 sure thing trustworthy unambiguous undoubted unequivocal unerring unmistakable verifiable

Antonyms

STRONGEST

counterfeit dishonest doubted doubtful false indefinite indistinct invalid obscure uncertain unclear unreal unsure vague

WEAK

doubting dubious faltering hesitant questionable unconfident undecided unfixed 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 doubting dubious faltering hesitant questionable unconfident undecided unfixed unpredictable unreliable unsure

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 ordinary unimportant usual

WEAK

doubtful doubting dubious faltering hesitant questionable uncertain unconfident undecided unfixed unpredictable unreliable unsure

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 thing I feel most certain about is that the technology is solved, and it is happening faster than people think.

From Barron's • Mar. 27, 2026

It was the most certain "yes" I have ever said in my life.

From BBC • Dec. 24, 2023

If so, I am most certain I will address this — in person!

From Washington Post • Jun. 29, 2022

You probably think that sense perception is the clearest and most certain way you can know the world around you.

From Textbooks • Jun. 15, 2022

But the motives of Faith are such, that although the Object be most certain, yet the Evidence is not so clear and irresistible, as that which flows from Sense, or a Demonstration.

From "The Invention of Science" by David Wootton