trĭennĭum, ii, n. (sc. spatium) [tres-annus],
the space of three years , three years : biennium aut triennium est, cum virtuti nuntium remisisti, Cic. Fam. 15, 16, 3; Plaut. Mil. 2, 3, 79; id. Most. 2, 2, 10; id. Stich. 1, 2, 80; 1, 3, 61; Cic. Q. Fr. 1, 1, 2, § 8; Caes. B. G. 4, 4; Auct. B. Afr. 19, 3 al.