Lewis & Short

sempĭternus, a, um, adj. [semper; like hesternus and aeternus, from heri and aevum], everlasting, ever-during, perpetual, continual, imperishable, eternal, sempiternal (cf. aeternus init.; very freq. and class.): fragile corpus animus sempiternus movet, etc., Cic. Rep. 6, 24, 26; cf. id. N. D. 3, 12, 29: immortalis memoria et sempiterna, Plaut. Mil. 3, 3, 15: deorum vita sempiterna, Ter. And. 5, 5, 3; cf.: aevo sempiterno frui, Cic. Rep. 6, 13, 13: ignes, id. ib. 6, 15, 15; cf.: cursus stellarum, id. ib. 6, 17, 17: gratias agere sempiternas, Plaut. Poen. 5, 4, 84: amicus, id. Most. 1, 3, 90; id. Pers. 1, 1, 36; cf.: verae amicitiae, Cic. Lael. 9, 32; so, hiemes, Varr. R. R. 1, 2, 4: ignis Vestae, Cic. Cat. 4, 9, 18: documentum Persarum sceleris, id. Rep. 3, 9, 15: memoria amicitiae nostrae, id. Lael. 4, 15: odia, id. ib. 10, 35: consilium senatus, id. Sest. 65, 137: potentia, Tac. A. 3, 30 et saep.: nihil umquam nisi sempiternum et divinum animo volutare, Cic. Rep. 1, 17, 28: nihil nisi sempiternum spectare, id. Rab. Perd. 10, 29: in sempiternum, forever, Vulg. Deut. 5, 29 et saep.
Adv., in three forms (not in Cic.), always, forever, perpetually.

      1. * a. sempĭ-ternum, Plaut. Aul. 2, 1, 26.
      2. b. sem-pĭternō, Cato ap. Charis. p. 194 P.: sempiterno permanet ea materia, Vitr. 1, 5; 9, 1, 2; Sol. 35, 5.
      3. c. sempĭternē, Pac. ap. Non. 170, 20; Claud. Mam. Stat. An. 1, 3.