cer·tain / ˈsərtn/ • adj. 1. known for sure; established beyond doubt: she looks certain to win an Oscar. ∎  having complete conviction about something; confident: are you absolutely certain about this?2. specific but not explicitly named or stated: the exercise was causing him a certain amount of pain. ∎  used when mentioning the name of someone not known to the reader or hearer: a certain General Percy captured the town.• pron. (certain of) some but not all: certain of his works have been edited.PHRASES: for certain without any doubt: I don't know for certain.make certain take action to ensure that something happens or is the case: I made certain that our paths would never cross again. ∎  establish whether something is definitely correct or true: he probably knew her, but it didn't do any harm to make certain.

certain fixed; sure XIII; some (particular or definite) XIII; established as truth; fully confident XIV; a certain XVIII; a certain age (after F. d'un certain âge rather elderly) XIX. — (O)F. :- Rom. *certānus, extension of L. certus settled, sure, pp. formation on cernere sift, separate, decide, rel. to Gr. krī́nein (see CRISIS).
So certainty XIV. — AN. certainté, OF. certaineté.