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1. sērĭus, a, um, adj. [perh. for sevrius; root sev-, severus; Gr. σέβας, σεμνός], grave, earnest, serious, opp. to sportive, jocular (class. only of things; severus, both of persons and things): res (opp. jocosae), Cic. Off. 1, 37, 134: sermo (opp. jocus), Auct. Her. 3, 14, 25: non res potissimum seria, sed quasi ludus ac jocus, Lact. 2, 18, 3: graves seriaeque res, Cic. Off. 1, 29, 103; so, res serias omnis extollo in alium diem, Plaut. Poen. 2, 51: ait rem seriam Velle agere mecum, Ter. Eun. 3, 3, 7; Liv. 23, 7 fin.: dies religiosus ad agendum quicquam rei seriae, id. 26, 17 al.: verba, Tib. 3, 6, 52; cf. Hor. A. P. 107: quaestiones, Suet. Calig. 32: carmina, Plin. Pan. 54, 2: curae, id. ib. 82 fin.: partes dierum, id. ib. 49 fin.: tempus, id. Ep. 4, 25, 3 et saep.: opinor hercle hodie quod ego dixi per jocum, Id eventurum esse et severum et serium, Plaut. Poen. 5, 3, 51: si aliquid serium, etc., Quint. 6, 3, 16: nec quicquam grave ac serium, Tac. A. 3, 50 fin.
With sup.: verba seria dictu, Hor. A. P. 107.
As subst.: sērĭum, i, and more freq. sērĭa, ōrum, n., earnestness, seriousness; serious matters or discourse (often opp. jocus); sing.: si quid per jocum Dixi, nolito in serium convortere, Plaut. Poen. 5, 5, 42: itaque res in serium versa est, Curt. 5, 7, 10: nihil ad serium, Tac. A. 6, 14.
Plur.: quīcum joca, seria, ut dicitur, Cic. Fin. 2, 26, 85: joca atque seria cum humillimis agere, Sall. J. 96, 2: cum his seria ac jocos celebrare, Liv. 1, 4 fin.: per seria per jocos, Tac. A. 2, 13: sed tamen amoto quaeramus seria ludo, Hor. S. 1, 1, 27; 2, 2, 125; id. A. P. 226; Ov. F. 5, 341 al.: mala, Hor. A. P. 451: mea (opp. lusus), Ov. Tr. 1, 8, 31: (Marsus) seria partitur in tria genera, Quint. 6, 3, 108: ille seria nostra, ille deliciae, Plin. Ep. 8, 1, 2.
Of persons, for severus (ante- and post-class.): non ego te novi tristem servum, serium? Afran. ap. Non. 33, 33: amicos serios aspernatur, App. Mag. 98, p. 336, 9: Solon, id. ib. 9, p. 278 fin.; Amm. 26, 2, 2; 29, 6, 1; Treb. Claud. 12, 5; Mam. Grat. Act. 12, 2; Quint. Decl. 15, 3.
Hence, adv. in two forms.
2. sērĭus, comp. adv., v. 3. sero.