based on custom rather than documentation; "an unwritten law"; "rites...so ancient that they well might have had their unwritten origins in Aurignacian times"- J.L.T.C.Spence
having been learned or found or determined especially by investigation
characterized by great determination; "a struggle against a determined enemy"
determined or decided upon as by an authority; "date and place are already determined"; "the dictated terms of surrender"; "the time set for the launching"
devoting full strength and concentrated attention to; "made continued and determined efforts to find and destroy enemy headquarters"
not counterfeit or copied; "an authentic signature"; "a bona fide manuscript"; "an unquestionable antique"; "photographs taken in a veritable bull ring"
conforming to fact and therefore worthy of belief; "an authentic account by an eyewitness"; "reliable information"