Lewis & Short

sīve (old orthog. SEIVE, Tab. Bantin. l. 6; and hence, by apocope, like neu, from neve, NEIVE). seu (the latter form very rare in Cic.; more freq. in Cæs.; as freq. as sive in the poets), conj. [si-ve], a disjunctive conditional particle, or if = vel si.

  1. I. Put once, preserving the conditional signif. of the si (cf., on the other hand, infra, II. B. 2.).
    1. A. After a preceding si (mostly ante-class.): si vivimus sive morimur, Enn. ap. Prisc. p. 880 P. (Ann. v. 384 Vahl.): si media nox est, sive est prima vespera, Plaut. Curc. 1, 1, 4: si ista uxor sive amica est, Ter. And. 1, 3, 11: si nocte sive luce, si servus sive liber faxit, Rogat. ap. Liv. 22, 10: si arborum trunci, sive naves essent a barbaris missae, Caes. B. G. 4, 17 fin.: si ego volo seu nolo, Plaut. Cist. 3, 14: si movero me, seu secari sensero, id. Merc. 2, 2, 40: si speras … seu tibi confidis, etc., id. Rud. 3, 2, 19; Val. Fl. 1, 837: si te, etc. … sive haec, etc. … seu, etc., Ter. And. 1, 5, 58.
    2. B. Without a preceding si (rare): dehinc postulo, sive aequom’st, te oro, ut, etc., Ter. And. 1, 2, 19 (for which: peto a te, vel si pateris, oro, Cic. Fam. 9, 13, 3): bis denas Italo texamus robore naves, Seu plures complere valent, etc., Verg. A. 11, 327: me seu corpus spoliatum lumine mavis, Redde meis, id. ib. 12, 935; cf.: haec pars dialectica, sive illam dicere malumus disputatricem, Quint. 12, 2, 13: turdus, Sive aliud privum dabitur tibi, devolet illuc, Hor. S. 2, 5, 11; cf. id. C. 1, 6, 19.
  2. II. Repeated, with a disjunctive sense predominant.
    1. A. Connecting words or phrases in the same construction. or conditional clauses which have the same predicate: sive (seu) … sive (seu) (in good prose, esp. in Cic., usually sive … sive; in Cæs. often seu … seu; after the Aug. period often sive … seu, or seu … sive); prop. if this or if that be the case, placing the counter propositions on an equality, be it that … or that; if … or if; whether … or, i. e. in either case (the predominant use and signif. in prose and poetry).
      1. 1. In gen.: qui improbus est, sive subbibit, sive adeo caret temeto, tamen ab ingenio est improbus, Plaut. Truc. 4, 3, 59; so, sive … sive etiam, Cic. Tusc. 4, 3, 6; Caes. B. C. 1, 27: sive quid mecum ipse cogito, sive quid aut scribo aut lego, Cic. Leg. 2, 1, 1: sive eum ex paludibus elicere sive obsidione premere posset, Caes. B. G. 7, 32: sive regi sive optimatibus serviant, Cic. Rep. 1, 35, 55: ex quo exardescit sive amor sive amicitia, id. Lael. 27, 100: sive tu medicum adhibueris, sive non adhibueris, id. Fat. 12 fin.; cf. id. Fam. 12, 2, 3: sive sub incertas Zephyris mutantibus umbras, Sive antro potius succedimus, Verg. E. 5, 5: seu recte, seu pervorse facta sunt, Egomet fecisse confiteor, Plaut. Trin. 1, 2, 146; Caes. B. C. 3, 61: facilem esse rem, seu maneant, seu proficiscantur, id. B. G. 5, 31; 5, 51; 7, 36; 7, 89; id. B. C. 3, 79; Sall. C. 49, 4; id. J. 103, 2; Verg. G. 3, 49; 4, 25; 4, 33; id. A. 2, 62; 6, 881 al.: quantitas plerumque eidem subjacet, seu modi est seu numeri, Quint. 7, 4, 41: sive dolo, seu jam Trojae sic fata ferebant, Verg. A. 2, 34: sive deae seu sint dirae volucres, id. ib. 3, 262; 4, 240; 7, 199; Liv. 10, 14; Quint. 1, 5, 18; 1, 5, 35; 1, 5, 41; 2, 1, 11; 12, 10, 26: seu magni superas jam saxa Timavi, Sive oram Illyrici legis aequoris, Verg. E. 8, 6; so, seu … sive, id. A. 1, 218; 10, 109; 11, 528; Ov. M. 4, 321; 4, 639; 15, 324 al. (In Cæs. B. C. 2, 27, the MSS. vary between seu … sive and sive … sive.)
      2. 2. Repeated several times: sive ancillam sive servum sive uxorem sive adulterum, Seu patrem sive avum videbo, Plaut. Am. 4, 5, 15 sq.; cf. id. ib. prol. 69 sq.; and id. Merc. 2, 2, 35: quibus (Cimmeriis) aspectum solis sive deus aliquis sive natura ademerat, sive loci situs, Cic. Ac. 2, 19, 61: seu furor est: habeo, quae carmine sanet et herbis; Sive aliquis nocuit: magico lustrabere ritu; Ira deum sive est: sacris placabimus iram, Ov. M. 10, 397 et saep.
      3. 3. With a corresp. si: sive tu vatem, sive tu omen audieris; sive immolaris, sive avem aspexeris; si Chaldaeum, si haruspicem videris, si fulserit, etc., Cic. Div. 2, 72, 149.
    2. B. Connecting complete conditional sentences, each with its own conclusion, but always implying that the alternative conclusions are alike steps in the general argument, if, on the one hand … if, on the other, if … but if: nam sive timuit, quid ignavius? sive meliorem suam causam fore putavit, quid injustius? Cic. Att. 8, 9, 3: sive enim ad sapientiam perveniri potest, non paranda nobis solum ea, sed fruenda etiam est; sive hoc difficile est, tamen nec modus est ullus investigandi, etc., id. Fin. 1, 1, 3: eis sive creditur, creditur hoc ipsum quod nos arguimus, sive fides non habetur, de adversarii testium fide derogatur, id. Caec. 1, 3; id. Tusc. 1, 18, 42: ut sive abstinuisset Epiro, integra sibi omnia essent: sive venisset, sic quoque spes veniae foret, Liv. 36, 6, 6 sq.; 36, 16, 10; 38, 3, 10; 37, 15, 2: eos seu dedi placeat, dedere se paratos esse, seu supplicio adfici, daturos poenas, id. 7, 20, 7; 27, 14, 1; 30, 40, 7.
      1. 2. Instead of sive as a correl., sin or si vero is sometimes found: sive sensus exstinguitur … quis me beatior? sin vera sunt quae dicuntur, migrationem esse, etc., Cic. Tusc. 1, 41, 97 sq.: sive enim Zenonem sequare, magnum est efficere … si vero Academiam veterem persequamur, etc., id. Ac. 1, 2, 7: sive enim abscedant, cui dubium esse quin, etc.; sin autem manendum ibi nihilo minus sit, Liv. 37, 15, 2.
      2. 3. In this use * si … sive is found once: si omnes atomi declinabunt, nullae umquam cohaerescent, sive aliae declinabunt, aliae suo nutu recte ferentur, primum, etc., Cic. Fin. 1, 6, 20 B. and K.; cf.: si … sive in one sentence, I. A. supra; and v. Madv. ad Cic. Fin. p. 45.
    3. C. On account of the predominant disjunctive sense,
      1. 1. In the poets and in post-Aug. prose, instead of one sive, sometimes aut, vel, or one of the interrogative particles ne or an is used: (saxum) seu turbidus imber Proluit, aut annis solvit sublapsa vetustas, Verg. A. 12, 685: sive … sive … vel, etc., Flor. 4, 2, 79: misero conjux, fatone erepta Creusa Substitit, erravitne viā, seu lassa resedit, Incertum, Verg. A. 2, 739: sive fatali vecordiā an, etc., Tac. A. 11, 26; so, sive … seu … an, id. ib. 14, 59.
      2. 2. Sometimes also sive stands alone in a purely disjunctive sense, = vel (in Cicero only in the phrases sive quis, sive potius, sive etiam): ut mihi Platonis illud, seu quis dixit alius, perelegans esse videatur, or whoever else said it, Cic. Rep. 1, 17, 29: quid perturbatius hoc ab urbe discessu, sive potius turpissimā fugā? id. Att. 8, 3, 3: te primum rogo, ut (animum) erigas ac resistas, sive etiam ultro occurras negotiis, id. Q. Fr. 1, 1, 1, § 4: Aristarchus et aetate nostrā Palaemon vocabulum, sive appellationem, nomini subjecerunt, Quint. 1, 4, 20: delectandi sive conciliandi officium, id. 12, 10, 59: miracula visa sive ex metu credita, Tac. A. 2, 24: proelium sive naufragium, Just. 2, 9, 20: Romana bella sive Asiana, id. 38, 3, 10.