certain

certain — adjective

1. feeling sure about something because you have good reasons to think it is true.

1.adjectiveB1
Definition

feeling sure about something because you have good reasons to think it is true.

Example

Ravi is certain that he locked the front door before leaving for work.

be certain + that-clause for personal conviction

Before the exam, Priya felt certain she had reviewed every chapter.

Common collocations
  • absolutely certain
  • fairly certain
  • quite certain
  • certain of
  • certain about
Synonyms
  • sure

    more common in everyday conversation; 'certain' sounds slightly more formal

  • confident

    focuses on self-assurance rather than objective truth

  • convinced

    implies someone has persuaded you of something

  • positive

    very strong certainty, used informally in British English

Antonyms
  • uncertain

    the direct opposite at the same register

  • doubtful

    implies you think something is probably not true

Grammar Patterns

be certain + that-clause

be certain + wh- word

be certain + of/about + noun

Usage Note

Often used with verbs of feeling such as 'feel', 'be', or 'seem'. The that-clause pattern is the most common in everyday speech.

Common Mistakes

I am certain to pass the test' (when expressing personal confidence).
I am certain that I passed the test.
'certain to' means something will definitely happen; 'certain that' expresses personal conviction about a fact.

2. established as a fact that nobody can reasonably question.

2.adjectiveC1
Definition

established as a fact that nobody can reasonably question.

Example

It is now certain that the volcano erupted at least three times in the past.

it is certain + that-clause for objective fact

Although nobody saw it happen, one thing is certain: a truck hit the fence.

Common collocations
  • it is certain that
  • far from certain
  • not yet certain
  • by no means certain
Synonyms
Antonyms
  • uncertain

    direct opposite at the same register

  • debatable

    implies reasonable people may disagree

Grammar Patterns

it is certain + that-clause

something is certain

Usage Note

Distinguish from sense 1: here the speaker is stating that something is objectively undisputed, not expressing a personal feeling. Frequently occurs in the impersonal pattern 'it is certain that…'.

Common Mistakes

I am certain that the earth is round' (personal conviction frame for an undisputed fact).
It is certain that the earth is round.
Use the impersonal structure for facts everyone agrees on.

3. so sure to happen that you cannot stop or avoid it.

3.adjectiveB1
Definition

so sure to happen that you cannot stop or avoid it.

Example

If you do not water the tomato plants, they are certain to die within days.

be certain + to-infinitive for inevitable result

The Tigers are certain to reach the finals after this season's unbeaten run.

Common collocations
  • almost certain
  • certain to happen
  • certain to win
  • certain to succeed
Synonyms
  • bound

    less formal, common in British English ('bound to happen')

  • sure

    everyday alternative ('sure to rain')

  • destined

    more dramatic, implies fate

Antonyms

Grammar Patterns

be certain + to-infinitive

be certain + that-clause

Usage Note

The to-infinitive pattern ('be certain to do') is the most frequent. Do not confuse with sense 1: 'He is certain to win' means winning is inevitable; 'He is certain that he will win' expresses his personal confidence.

Common Mistakes

I am certain to like the movie' (using inevitable frame for a personal opinion).
I am certain that I will like the movie.
Use sense 1's that-clause for personal conviction; reserve 'certain to' for true inevitability.

4. used before a person's name when you have named them but the listener does not k

4.adjective
Definition

used before a person's name when you have named them but the listener does not know who they are.

Example

A certain Dr. Okafor from the university called while you were out.

a certain + title + name for unknown person

The letter was signed by a certain Ms. Leila Chen whom I had never met.

Common collocations
  • a certain Mr.
  • a certain Ms.
  • a certain Dr.
Synonyms
  • some

    more informal and dismissive ('some guy named Tom')

Grammar Patterns

a certain + name

Usage Note

Always appears before a personal name with the indefinite article 'a'. The tone often suggests the speaker has little or no personal knowledge of the person named.

5. present to a noticeable but not very large degree.

5.adjective
Definition

present to a noticeable but not very large degree.

Example

The work requires a certain level of skill with computer software.

a certain level/degree of + uncountable noun

Hana felt a certain sadness as she said goodbye to her childhood home.

a certain + abstract emotion noun

Common collocations
  • a certain amount
  • a certain degree
  • a certain level
  • a certain charm
Synonyms

Grammar Patterns

a certain + noun

a certain amount/degree of + noun

Usage Note

Often used with abstract nouns (sadness, charm, appeal, risk) or quantity nouns (amount, level, degree). The emphasis is on the vagueness or the difficulty of being more precise.

Idioms

for certain

idiom

Without any doubt or uncertainty.

Maya knew for certain that she had passed the exam.

Can you say for certain when the train will leave?

make certain (that…)

idiom

To check or confirm that something is definitely true or will happen.

Brian called the hotel to make certain his reservation was confirmed.

Make certain that you turn off the lights before leaving.

make certain of something/of doing something

idiom

To take action to ensure that something happens or is achieved.

Sara left early to make certain of catching the last bus.

Diego studied hard to make certain of passing the final exam.

of a certain age

idiom

Describes a person who is no longer young but not yet old, typically middle-aged.

The magazine targets readers of a certain age who enjoy travel.

Many people of a certain age prefer comfortable shoes.

certain — determiner

certain — pronoun

Word family

Synonym discussion

Sense: adjective/1

All four words describe a state of being free from doubt, but they differ in focus and register. 'Sure' is the most common and neutral in everyday conversation ('I am sure the train stops here') and works in almost any context. 'Certain' is slightly more formal and often implies a stronger basis of evidence ('The doctor is certain the test results are accurate'). 'Confident' leans toward self-assurance about a future outcome or one's own ability ('She feels confident about the presentation tomorrow'); it does not usually assert a factual claim. 'Convinced' suggests that the person has been persuaded by arguments or evidence ('After hearing the witness, the jury was convinced of his innocence'). 'Positive' is an informal intensifier common in British English ('Are you positive you locked the door?'), carrying the sense of absolute certainty. When you want to emphasise that your belief rests on solid reasons, use 'certain' or 'convinced'; in casual speech, 'sure' is the safest choice; for future-oriented self-belief, choose 'confident'; and for emphatic denial of any possibility of error, use 'positive'.

sure ↗confident ↗convinced ↗positive ↗

Common collocations

Nouns

Adverbs

Phrases

Prepositions

Etymology

LatinFrenchEnglish

The word 'certain' entered English through Old French 'certain', which came from the Latin 'certus', meaning 'sure, fixed, resolved'. The Latin root 'certus' is the past participle of 'cernere', meaning 'to distinguish, decide, or sift'. This older sense of separating or deciding is still faintly echoed in the way 'certain' picks out specific items from a larger group. The word has been in English since the 13th century, initially carrying the meaning of 'determined' or 'fixed' before developing its modern sense of 'known for sure'.