having a genuine original or authority, in opposition to that which is false, fictitious, counterfeit, or apocryphal; being what it purports to be; genuine; not of doubtful origin; real; as, an authentic paper or register.-authoritative.-of approved authority; true; trustworthy; credible; as, an authentic writer; an authentic portrait; authentic information.-vested with all due formalities, and legally attested.-having as immediate relation to the tonic, in distinction from plagal, which has a correspondent relation to the dominant in the octave below the tonic.-an original (book or document).