I.a leader, conductor, guide (for syn. cf.: imperator, ductor, tyrannus, rex, princeps, praetor, auctor).
I. In gen.: “illis non ducem locorum, non exploratorem fuisse,” Liv. 9, 5, 7; cf. “itineris,” Curt. 5, 4: “itinerum,” Caes. B. G. 6, 17, 1: “regendae civitatis (with auctor publici consilii),” Cic. de Or. 3, 17, 63: “dux isti quondam et magister ad despoliandum Dianae templum fuit,” Cic. Verr. 2, 3, 21: “nil desperandum Teucro duce et auspice Teucro,” Hor. C. 1, 7, 27: “tu dux et comes es,” Ov. Tr. 4, 10, 119; id. P. 4, 12, 23 et saep. —In the fem., Cic. Fin. 1, 21, 71; id. Lael. 5, 19; id. Div. 2, 40; id. Tusc. 1, 12, 27; Verg. A. 1, 364; Ov. M. 3, 12; 14, 121 et saep.—
II. In partic., in milit. lang., a leader, commander, general-in-chief.
A. Prop., Caes. B. G. 1, 13, 2; 2, 23, 4 (with qui summam imperii tenebat); 3, 18, 7; “3, 23, 3 et saep.—Prov.: ducis in consilio posita est virtus militum,” Pub. Syr. 136 (Rib.). Also a lieutenant-general, general of division (cf. duco, I. B. 5. b., and imperator), as opp. to the imperator, Caes. B. G. 3, 21, 1; Cic. Off. 3, 26, 99; id. Fl. 12, 27; Tac. H. 3, 37 al.—
B. Transf. beyond the milit. sphere, a leader, chief, head: “dux regit examen,” Hor. Ep. 1, 9, 23; cf. “gregis, i. e. aries,” Ov. M. 5, 327; 7, 311; so, “pecoris,” Tib. 2, 1, 58; “but dux gregis = pastor,” id. 1, 10, 10: “armenti, i. e. taurus,” Ov. M. 8, 884; “of the head of a sect of philosophers,” Lucr. 1, 638; cf. Quint. 5, 13, 59; Hor. Ep. 1, 1, 13.