Lewis & Short

septēni, ae, a (gen. plur. only septenūm, Cic. Verr. 2, 2, 49, § 122; Col. 12, 28, 1), num. distrib. adj. [septem].

  1. I. Seven each: a summo septenis cyathis committe hos ludos, Plaut. Pers. 5, 1, 19: duo fasces, candelis involuti, septenos habuere libros, Liv. 40, 29; Col. 1, 3, 10; Plin. 7, 25, 25, § 91 (dub.); 17, 10, 11, § 64.
    Gen.: amphorarum septenum, Col. 12, 28, 1: pueri annorum senum septenumque denum, Cic. Verr. 2, 2, 49, § 122.
  2. II. Transf., for septem, seven: dispar septenis fistula cannis, Ov. M. 2, 682: fila lyrae, id. F. 5, 105: quā septenas temperat unda vias (the seven mouths of the Nile), Prop. 3 (4), 22, 16; cf. in the foll.: homo crescit in longitudinem ad annos usque ter septenos, Plin. 11, 37, 87, § 216: bis septenos greges, Sen. Herc. Oet. 1850.
    Sing., sevenfold (poet. and in postAug. prose): gurgite septeno rapidus mare submovet amnis (Nilus), Luc. 8, 445: gurges Nili, Claud. in Rufin. 1, 185: Ister (the seven-mouthed Danube), Stat. S. 5, 2, 136 (cf. septemplex): non removeri septeno circuitu, Plin. 28, 16, 66, § 228.