Synonyms of certain

certain

adjective

ˈsər-tᵊn 

1

as in one

known but not named

a certain person told me that today is your birthday

Synonyms & Similar Words

• one
• some
• unnamed
• unspecified
• anonymous
• specific
• unidentified
• given
• particular

Antonyms & Near Antonyms

• known
• named
• specified

2

as in sure

having or showing a mind free from doubt

I'm certain that they'll arrive on time

Synonyms & Similar Words

• sure
• confident
• positive
• assured
• doubtless
• implicit
• clear
• sanguine
• cocksure
• resolute
• decisive
• self-assured
• self-confident
• unwavering
• unquestioning
• unfaltering
• unhesitating
• self-conceited

Antonyms & Near Antonyms

• uncertain
• doubtful
• unsure
• dubious
• hesitant
• indecisive
• unassuming
• wavering
• vacillating
• diffident

3

as in stable

having been established and usually not subject to change

a certain percentage of the profits will go to charity

Synonyms & Similar Words

• stable
• final
• fixed
• unchanging
• unchangeable
• determinate
• set
• hard
• specific
• frozen
• firm
• settled
• flat
• hard-and-fast
• constant
• steady
• definite
• uniform
• inexpugnable
• explicit
• exact
• good
• sure
• given
• true
• stipulated
• reliable
• stated
• responsible
• safe
• dependable
• nonnegotiable
• solid
• noncancelable
• nonadjustable
• unwavering
• trustworthy
• tried
• trusty
• tried-and-true

Antonyms & Near Antonyms

• adjustable
• negotiable
• changeable
• unspecified
• indefinite
• uncertain
• variable
• volatile
• unpredictable
• fluid
• unstable
• capricious
• fluctuating
• mercurial
• temperamental
• mutable
• unsettled
• inconstant
• unsteady
• open-ended
• changeful
• flickery

4

as in necessary

impossible to avoid or evade

as he got older, the athlete began to feel the certain effects of the aging process on his body

Synonyms & Similar Words

• necessary
• inevitable
• possible
• definite
• unavoidable
• sure
• inescapable
• probable
• ineluctable
• destined
• unescapable
• in the cards
• likely
• in the bag
• decided
• ineludible
• relentless
• settled
• predetermined
• fated
• inexorable
• preordained
• predestined
• unremitting
• unstoppable
• foreordained

Antonyms & Near Antonyms

• uncertain
• unsure
• doubtful
• avoidable
• questionable
• unclear
• dubious
• preventable
• unlikely
• shaky
• evadable
• undecided
• unreliable
• unsettled
• improbable
• undependable

5

as in reliable

not likely to fail

chicken soup is grandma's certain cure for pretty much whatever ails you

Synonyms & Similar Words

• reliable
• sure
• surefire
• infallible
• unfailing
• deadly
• dependable
• can't-miss
• fail-safe
• unerring

Antonyms & Near Antonyms

• uncertain
• doubtful
• questionable
• fallible

6

as in definite

not capable of being challenged or proved wrong

up to this point there's been no certain evidence that a crime has been committed

Synonyms & Similar Words

• definite
• positive
• sure
• conclusive
• unquestionable
• undeniable
• indubitable
• indisputable
• incontestable
• irrefutable
• incontrovertible
• unanswerable
• unarguable
• irrefragable
• accomplished
• unchallengeable
• inarguable
• absolute
• unambiguous
• unequivocal
• clear
• decisive
• undisputed
• unquestioned
• uncontested
• uncontradicted
• hands-down

Antonyms & Near Antonyms

• problematic
• questionable
• arguable
• debatable
• controversial
• negotiable
• uncertain
• disputable
• answerable
• moot
• disputed
• doubtful
• dubious
• ambiguous
• controvertible
• inconclusive
• theoretical
• refutable
• doubtable
• contradictable
• academic
• indecisive
• hypothetical
• speculative
• debated
• iffy
• equivocal

Synonym Chooser

How does the adjective certain contrast with its synonyms?

Some common synonyms of certain are cocksure, positive, and sure. While all these words mean "having no doubt or uncertainty," certain may apply to a basing of a conclusion or conviction on definite grounds or indubitable evidence.

police are certain about the cause of the fire

When would cocksure be a good substitute for certain?

In some situations, the words cocksure and certain are roughly equivalent. However, cocksure implies presumptuous or careless positiveness.

you're always so cocksure about everything

When is it sensible to use positive instead of certain?

While the synonyms positive and certain are close in meaning, positive intensifies sureness or certainty and may imply opinionated conviction or forceful expression of it.

I'm positive that's the person I saw

When could sure be used to replace certain?

The words sure and certain are synonyms, but do differ in nuance. Specifically, sure usually stresses the subjective or intuitive feeling of assurance.

felt sure that I had forgotten something

Example Sentences

Recent Examples of certain

The insects also develop in quince and are reported to be incidental in plums, pears, tart cherries, and certain other members of the rose family. — Encyclopedia Britannica, 29 Sep. 2026

But after an initial surge in interest in Turning Point, with new chapters popping up at high schools and colleges across the country, the future of the organization in a fracturing MAGA movement now seems less certain one year later. — Clara Molot, Vanity Fair, 29 Sep. 2026

The fate of the bill is not yet certain, but Newsom only has until the end of the Wednesday to sign or veto it. — Stephen Hobbs, Sacbee.com, 29 Sep. 2026

Meta Platforms established an independent board in 2018 to weigh Facebook users’ complaints about decisions to block certain content. — Business Columnist, Los Angeles Times, 29 Sep. 2026

Phrases Containing certain

• for certain
• of a certain age