Certain

Assured in mind; having no doubts; free from suspicions concerning.

Determined; resolved; -- used with an infinitive.

Not to be doubted or denied; established as a fact.

Actually existing; sure to happen; inevitable.

Unfailing; infallible.

Fixed or stated; regular; determinate.

Not specifically named; indeterminate; indefinite; one or some; -- sometimes used independenty as a noun, and meaning certain persons.

Certainty.

A certain number or quantity.

Certainly.

established beyond doubt or question; definitely known; "what is certain is that every effect must have a cause"; "it is certain that they were on the bus"; "his fate is certain"; "the date for the invasion is certain"

having or feeling no doubt or uncertainty; confident and assured; "felt certain of success"; "was sure (or certain) she had seen it"; "was very sure in his beliefs"; "sure of her friends"