Lewis & Short

ŏb (old form obs, v. III.), prep. with acc. (in late Lat. also with the abl.: OB PERPETVO EIVS ERGA SE AMORE, Inscr. Orell. 106) [Osc. op; kindr. with Sanscr. api; Gr. ἐπί].

  1. I. Lit.
    1. A. With verbs of motion, towards, to (only ante-class.): IS TERTHS DIEBVS OB PORTVM OBVAGVLATVM ITO, let him go before his house to summon him, Fragm. XII. Tab. ap. Paul. ex Fest. s. v. portum, p. 233 Müll.: ob Romam legiones ducere, Enn. ap. Paul. ex Fest. p. 179 Müll. (Ann. v. 295 Vahl.); cf.: ob Troiam duxit, id. ib. p. 178 Müll. (Incert. libr. v. 5 Vahl.): cujus ob os Grai ora obvertebant sua, Poët. ap. Cic. Tusc. 3, 18, 39; and ap. Cic. Fam. 9, 26, 2 (Trag. Rel. p. 211 Rib.).
    2. B. With verbs of rest, about, before, in front of, over (in Cic.): follem sibi obstringit ob gulam, Plaut. Aul. 2, 4, 23: lanam ob oculum habere, id. Mil. 5, 37: ob oculos mihi caliginem obstitisse, before my eyes, id. ib. 2, 4, 51: mors ob oculos saepe versata est, Cic. Rab. Post. 14, 39; id. Sest. 21, 47: ignis qui est ob os offusus, id. Univ. 14.
  2. II. Transf., to indicate the object or cause, on account of, for, because of, by reason of, etc.
    1. A. In gen. (freq. and class.): etiam ob stultitiam tuam te tueris? do you still defend yourself with regard to your folly? Plaut. Trin. 3, 2, 82: pretium ob stultitiam fero, Ter. And. 3, 5, 4; id. Phorm. 2, 3, 23: ob eam rem iratus, on that account, Plaut. Bacch. 4, 4, 33: neu quid ob eam rem succenseat, id. ib. 4, 4, 39; Ter. Ad. 5, 6, 7: Mi. Ob eam rem? De. Ob eam, id. ib. 5. 9, 20: ob rem nullam, id. Hec. 5, 3, 2: hanc Epicurus rationem induxit ob eam rem, quod veritus est, ne, etc., Cic. Fat. 10, 23: ob eam causam, quod, etc., id. Rep. 1, 7, 12: quam ob causam venerant, id. de Or. 1, 7, 26: non solum ob eam causam fieri volui, quod, etc., id. Rep. 1, 21, 34: ob hanc causam, quod, id. ib. 2, 1, 3: nec ob aliam causam ullam, etc., id. Lael. 20, 74: ob meas injurias, Ter. Heaut. 1, 1, 85; cf.: quodnam ob facinus? id. ib. 5, 2, 3: ob peccatum hoc. id. ib. v. 37: ob malefacta haec, id. Ad. 2, 1, 46: ob illam injuriam, Cic. Rep. 2, 25, 46: ob aliquod emolumentum suum, id. Font. 8, 17: (eum) ac Troiam misi ob defendendam Graeciam, Enn. ap. Cic. Tusc. 3, 13, 28 (Trag. v. 362 Vahl.): ob rem judicandam pecuniam adcipere, Cic. Verr. 2, 2, 32, § 78; id. Att. 1, 17, 8; id. Mur. 1, 1; id. Verr. 2, 2, 48, § 119; Sall. J. 89, 2; Quint. 5, 10, 87: nec meliores ob eam scientiam nec beatiores esse possumus, on account of, for that knowledge, Cic. Rep. 1, 19, 32: ob eam (amicitiam) summā fide servatam, id. Lael. 7, 25: is igitur dicitur ab Amulio ob labefactandi regni timorem, ad Tiberim exponi jussus esse, id. Rep. 2, 2, 4: unius ob iram Prodimur, Verg. A. 1, 251; cf.: saevae memorem Junonis ob iram, id. ib. 1, 4; cf. also: aut ob avaritiam aut miserā ambitione laborat, Hor. S. 1, 4, 26: barbarus eum quidam palam ob iram interfecti ab eo domini obtruncat, Liv. 21, 2, 6: non noxā neque ob metum, Tac. H. 2, 49: Germanicum mortem ob rem publicam obiisse, for the republic, id. A. 2, 83: cum quibus ob rem pecuniariam disceptabat, id. ib. 6, 5.
    2. B. In partic.
      1. 1. In consideration of, in return for, instead of (mostly ante-class.): ob asinos ferre argentum, Plaut. As. 2, 2, 80; id. Ep. 5, 2, 38: quin arrhabonem a me accepisti ob mulierem? id. Rud. 3, 6, 23: ager oppositus est pignori Ob decem minas, Ter. Phorm. 4, 3, 56: talentum magnum ob unam fabulam datum esse, C. Gracch. ap. Gell. 11, 10 fin.: pecuniam ob absolvendum accipere, Cic. Verr. 2, 2, 32, § 78: pecuniam ob delicta dare, Tac. A. 14, 14.
      2. 2. Ob rem, like ex re (opp. frustra), to the purpose, with advantage, profitably, usefully (very rare): An. Non pudet Vanitatis? Do. Minime, dum ob rem, Ter Phorm. 3, 2, 41: verum id frustra an ob rem faciam, in vostrā manu situm est, Sall. J. 31, 5.
      3. 3. Ob industriam, on purpose, intentionally, Plaut. Cas. 4, 3, 6; 2, 3, 58 (id. ib. 2, 3, 60, de industriā); cf. id. Men. 1, 2, 14.
      4. 4. Quam ob rem, also written in one word, quamobrem, on which account, wherefore, therefore, hence, accordingly; a very freq. particle of transition, esp. in Cic.: quam ob rem id primum videamus, quatenus, etc., Cic. Lael. 11, 36: quam ob rem utrique nostrūm gratum admodum feceris, id. ib. 4, 16; 2, 10; 3, 12; 4, 15; id. Rep. 1, 5, 9; 1, 19, 32 et saep.
      5. 5. Ob id, ob hoc, ob haec, ob ea, ob quae, on that account, therefore (not ante-Aug.).
        1. a. Ob id: ignaris hostibus et ob id quietis, Liv. 25, 35; 28, 2; Tac. A. 2, 66; 3, 75; 13, 5: ob id ipsum, Curt. 4, 16, 23.
        2. b. Ob hoc: ob hoc cum omnia neglecta apud hostes essent, Liv. 25, 37; Sen. Q. N. 7, 14, 4; Col. 7, 3, 21; cf.: ob hoc miserior, Sen. Ep. 98, 5.
        3. c. Ob haec: ob haec cum legatos mitti placuisset, Liv. 8, 23; 21, 50; 38, 34; Cels. 1 praef.
        4. d. Ob ea: ob ea consul Albinus senatum de foedere consulebat, Sall. J. 39, 2.
        5. e. Ob quae: ob quae posterum diem reus petivit, Tac. A. 2, 30 fin.; Suet. Ner. 13.
  3. III. In composition, the b of ob remains unchanged before vowels and most consonants; only before p, f, c, g, is assimilation more common: oppeto, offero, occido, ogganio, etc.
    An ancient form obs, analogous to abs, is implied in obs-olesco and os-tendo.
    In signification, that of direction towards, or of existence at or before a thing is predominant, although it likewise gives to the simple verb the accessory notion of against: obicere, opponere, obrogare.