sure, certain, positive, cocksure mean having no doubt or uncertainty. sure usually stresses the subjective or intuitive feeling of assurance. certain may apply to a basing of a conclusion or …

CERTAIN definition: 1. having no doubt or knowing exactly that something is true, or known to be true, correct, exact…. Learn more.

CERTAIN definition: free from doubt or reservation; confident; sure. See examples of certain used in a sentence.

1. (postpositive) positive and confident about the truth of something; convinced: I am certain that he wrote a book. 2. (usually postpositive) definitely known: it is certain that they were on the …

If you are certain about something, you firmly believe it is true and have no doubt about it. If you are not certain about something, you do not have definite knowledge about it.

[before a noun] (used before a person or thing that is known in the mind of the speaker or writer, but that is being introduced to the listener): A certain Mr. Smith has been trying to meet you.

Dec 14, 2025 · certain (of indefinite, unknown or simply unmentioned identity, quality or quantity) (prepositive to the noun it modifies, and usually preceded by an indefinite article)