vīcēsimus or vīcensimus (collat. form vīgēsimus, Varr. R. R. 3, 9, 21; Caes. B. C. 3, 34; Sall. C. 47, 2; Col. 5, 1, 10; Manil. 4, 462 al.; but not in Cic.), a, um, ord. num. adj. [viginti], the twentieth. Adj.: annus, Plaut. Capt. 5, 3, 3: intra annum vicesimum, Caes. B. G. 6, 21: annum jam tertium et vicesimum regnat, Cic. Imp. Pomp. 3, 7: censores vicesimi sexti a primis censoribus, Liv. 10, 47, 2: litteras mihi Cornificius altero vicesimo die reddidit, Cic. Fam. 12, 25, 1: Acastus cum litteris praesto fuit uno et vicesimo die, id. ib. 14, 5: vicesimo die lunae, id. Fin. 2, 31, 101: vicesima luna sacrificant, Plin. 35, 2, 2, § 5: sexto et vicesimo anno, Nep. Lys. 1, 1: legio, Tac. A. 1, 51.

— Subst.: vīcēnsi-ma (-suma), ae, f. (i. e. pars), the twentieth part, as a tax; so the twentieth part or five per cent. of the crop, Liv. 43, 2, 12 Weissenb. ad loc.; of the value of a slave that was manumitted, Cic. Att. 2, 16, 1; Liv. 7, 16, 7; Petr. 58; 71.

—Called also VICESIMA LIBERTATIS, Inscr. Orell. 3131; 3338.

—As exportduty: portorii, Cic. Verr. 2, 2, 75, § 185.

— As a tax on inheritances, Plin. Ep. 7, 14, 1; id. Pan. 37.