What is a synonym for the word certain?

Answer 1

In the sense of "known for sure" or "sure of one's knowledge of something": sure, confident, positive, convinced, in no doubt, satisfied, assured, persuaded, indubitable, undeniable, irrefutable, indisputable; obvious, evident, recognized, confirmed, accepted, acknowledged, undisputed, undoubted, unquestioned.

In the sense of "specific but not explicitly named or stated" (as in "There are certain flaws in your plan"): particular, specific, individual, special.

In the sense of certain defeat (as in "The seven old men faced certain death as they headed into battle against the army of 250,000 soldiers."): inevitable, assured, destined, predestined; unavoidable, inescapable, inexorable, ineluctable.