Lewis & Short

aeternus, a, um, adj. [contr. from aeviternus, Varr. L. L. 6, § 11 Müll., from aevum, with the termination -ternus as in sempiternus, hesternus], without beginning or end, eternal (sempiternus denotes what is perpetual, what exists as long as time endures, and keeps even pace with it; aeternus, the eternal, that which is raised above all time, and can be measured only by œons (αἰῶνες, indefinite periods); for Tempus est pars quaedam aeternitatis, Cic. Inv. 1, 27, 39. Thus the sublime thought, without beginning and end, is more vividly suggested by aeternus than by sempiternus, since the former has more direct reference to the long duration of the eternal, which has neither beginning nor end. Sempiternus is rather a mathematical, aeternus a metaphysical, designation of eternity, Doed. Syn. I. p. 3).

  1. I. Lit.
    1. A. Of the past and future, eternal: deus beatus et aeternus, Cic. Fin. 2, 27, 88: nihil quod ortum sit, aeternum esse potest, id. N. D. 1, 8: O Pater, o hominum rerumque aeterna Potestas, Verg. A. 10, 18: di semper fuerunt, nati numquam sunt, siquidem aeterni sunt futuri, Cic. N. D. 1, 32, 90: idem legis perpetuae et aeternae vim Jovem dicit esse, id. ib. 1, 15, 40: nomen Domini Dei aeterni, Vulg. Gen. 21, 33; ib. Rom. 16, 26: aeternum tempus, Lucr. 1, 582: causae immutabiles eaeque aeternae, Cic. Fat. 12, 48.
    2. B. Of the future, everlasting, endless, immortal: natura animi … neque nata certe est et aeterna est, Cic. Tusc. 1, 23: virorum bonorum mentes divinae mihi atque aeternae videntur esse, id. Rab. 29: aeternam timuerunt noctem, Verg. G. 1, 468: Quod semper movetur, aeternum est, Cic. Tusc. 1, 23: Quidquid est illud quod sentit … caeleste et divinum ob eamque rem aeternum sit, necesse est, id. ib. 1, 27: ut habeam vitam aeternam, Vulg. Matt. 19, 16; ib. Joan. 3, 15; ib. Rom. 2, 7: in sanguine testamenti aeterni, ib. Heb. 13, 20: tu Juppiter bonorum inimicos aeternis suppliciis vivos mortuosque mactabis, Cic. Cat. 2, 13: ibunt in supplicium aeternum, Vulg. Matt. 25, 46: aeternas poenas in morte timendumst, Lucr. 1, 111: mitti in ignem aeternum, Vulg. Matt. 18, 8.
    3. C. Of the past: ex aeterno tempore quaeque Nunc etiam superare necessest corpora rebus, from eternity, Lucr. 1, 578: motum animorum nullo a principio, sed ex aeterno tempore intellegi convenire, Cic. Fin. 1, 6.
    4. D. Spec. of objects of nature, which the ancients regarded as stable and perpetual, everlasting, eternal: aeterna templa caeli, Poët. ap. Varr. L. L. 6, 11, p. 77 Müll.: aeternam lampada mundi, Lucr. 5, 402: micant aeterni sidera mundi, id. 5, 514: aeterna domus, i. e. caelum, Cic. Rep. 6, 23: donec veniret desiderium collium aeternorum, the everlasting hills, Vulg. Gen. 49, 26; ib. Ps. 75, 5; cf. ib. Ps. 103, 5.
  2. II. Meton., of indef. long time.
    1. A. Of the future, lasting, enduring, everlasting, perpetual: aeterni parietes, Plin. 35, 14, 49, § 172: dehinc spero aeternam inter nos gratiam fore, Ter. Eun. 5, 2, 33: aeternus luctus, Lucr. 3, 924: dolor, id. 3, 1003: vulnus, id. 2, 369; so Verg. A. 1, 36: aerumna, Cic. Sen. 34: mala, Verg. Cul. 130: bellum, Cic. Cat. 4, 22: dedecus, id. Font. 88: imperium, id. Rab. 33; so Verg. A. 1, 230: versūs, Lucr. 1, 121: ignis sacerdotis, Cic. Font. 47: gloria, id. Cat. 4, 21: laus, id. Planc. 26: memoria, id. Verr. 4, 69: non dubitat Lentulum aeternis tenebris vinculisque mandare, id. Cat. 4, 10.
      Comic.: spero me ob hunc nuntium aeternum adepturum cibum, Plaut. Capt. 4, 1, 13. Esp. of Rome: aeterna urbs, the Eternal City, Tib. 2, 5, 23; Ov. F. 3, 72; Cod. Th. 10, 16, 1; Symm. Ep. 3, 55; Inscr. Orell. 2, 1140.
      Comp.: nec est ulli ligno aeternior natura. Plin. 14, 1, 2, § 9: aeterniora mala, Lact. Epit. 9.
    2. B. Of the past, of yore, of old: ablue corpus alluvii aeternisque sordibus squalidum, Curt. 4, 1, 22.
  3. III. Adv. phrases.
      1. 1. in aeter-num.
    1. A. Lit., forever, everlastingly: et vivat in aeternum, Vulg. Gen. 3, 22: hoc nomen mihi est in aeternum, ib. Exod. 3, 15: Dominus in aeternum permanet, ib. Psa. 9, 8: vivet in aeternum, ib. Joan. 6, 52: Tu es sacerdos in aeternum, ib. Heb. 5, 6: non habebit remissionem in aeternum, ib. Marc. 3, 29.
    2. B. Meton., of indef. long time, forever, always: urbs in aeternum condita, Liv. 4, 4: leges in aeternum latae, id. 34, 6: (proverbia) durant in aeternum, Quint. 5, 11, 41: delatores non in praesens tantum, sed in aeternum repressisti, Plin. Pan. 35: (famulos) possidebitis in aeternum, Vulg. Lev. 25, 46: (servus) serviet tibi usque in aeternum, ib. Deut. 15, 17: ut sceleris memoria maneat in aeternum, Lact. 1, 11.
      1. 2. aeternum.
    1. A. Lit., forever: sedet aeternumque sedebit Infelix Theseus, Verg. A. 6, 617: ut aeternum illum reciperes, Vulg. Phil. 15 (prob. here an adv.).
    2. B. Meton., of indef. long time, forever, always: serviet aeternum, Hor. Ep. 1, 10, 41.
    3. C. Of what is continually repeated, constantly, again and again (as in colloq. Engl., everlastingly, eternally): glaebaque versis Aeternum frangenda bidentibus, Verg. G. 2, 400: ingens janitor Aeternum latrans (of Cerberus), id. A. 6, 401.
      1. 3. aeternō, meton., of indef. long time, forever, perpetually: viret aeterno hunc fontem igneum contegens fraxinus, Plin. 2, 107, 111, § 240: BVSTA TVTA AETERNO MANEANT, Inscr. Orell. 4517.