Lewis & Short

factĭo, ōnis, f. [facio].

  1. I. A making, doing, preparing (very rare): tabulae, quas is instituisset, cui testamenti factio nulla est, the right of making a will, Cic. Top. 11, 50; cf.: factionem testamenti habere, id. Fam. 7, 21: quae haec factio est? conduct, dealing, proceeding, Plaut. Rud. 5, 3, 15; id. Bacch. 4, 8, 2.
  2. II. (Acc. to facio, II. B.; lit., a taking part or siding with any one; hence concr.) A company of persons associated or acting together, a class, order, sect, faction, party (syn.: pars, partes, causa, rebellio, perduellio, seditio).
    1. A. In gen. (rare): cum vostris nostra non est aequa factio; Affinitatem vobis aliam quaerite, i. e. family, rank, Plaut. Trin. 2, 4, 51; cf.: neque nos factione tanta, quanta tu, sumus, id. Cist. 2, 1, 17; id. Trin. 2, 4, 66; 90; 96; id. Aul. 2, 1, 45: utrimque factiones tibi pares, Cato ap. Charis. p. 198 P.: alia (medicorum) factio coepit in Sicilia, i. e. class or school, Plin. 29, 1, 4, § 5: est et alia magices factio, a Mose pendens, id. 30, 1, 2, § 11: lascivientium, Vulg. Amos, 6, 7.
    2. B. In partic., a company of political adherents or partisans, a party, side, faction (class.; among the republican Romans usually with the odious accessory notion of oligarchical): in Gallia non solum in omnibus civitatibus atque in omnibus pagis partibusque, sed paene etiam in singulis domibus factiones sunt, earumque factionum principes sunt, qui, etc., divisions, factions, Caes. B. G. 6, 11, 2 sq.: paucorum factione oppressus, id. B. C. 1, 22, 5; cf.: in qua (Scaevolae oratione) invidia incitatur in judicum et in accusatorum factionem, Cic. Brut. 44, 164: haec inter bonos amicitia, inter malos factio est, Sall. J. 31, 15: conspiratis factionum partibus, Phaedr. 1, 2, 4: per vim et factionem, Cic. Att. 7, 9, 4: triginta illorum consensus et factio, i. e. oligarchy, Cic. Rep. 1, 28; cf.: cum certi propter divitias aut genus aut aliquas opes rem publicam tenent, est factio: sed vocantur illi optimates, id. ib. 3, 14; 1, 44; cf. also: ut exsistat ex rege dominus, ex optimatibus factio, ex populo turba et confusio, id. ib. 1, 45: in factionis potestate, id. ib. 3, 32: principem factionis ad Philippum trahentium res, Liv. 32, 19, 2; Tac. H. 1, 13; Suet. Claud. 13.
      1. 2. Scenic t. t., a division, company, or party of charioteers at the Roman races (of which there were four, named after their colors: albata, prasina, russata, veneta), Suet. Calig. 55; id. Vit. 7; 14; id. Dom. 7; Inscr. Orell. 2593; cf. Fest. p. 86 Müll.; and Anthon’s Dict. of Antiq. p. 256.
        Also of pantomimes, Suet. Ner. 16; and: domini factionum = factionarii, id. ib. 5; 22; Lampr. Com. 16.