necessary (adj.) Copy link Outline I. Indispensably requisite1. nĕcessārius2. nĕcessĕ, indecl. (with esse and habere)3. ŏpus, indecl. (need, needfulII. Inevitable • necessary (adj.): I. Indispensably requisite: 1. nĕcessārius: everything n. to life, omnia quae ad vitam n. sunt, Cic. Off. 1, 4, init. 2. nĕcessĕ, indecl. (with esse and habere): buy not what you want, but what is n., emas non quod opus est, sed quod n. est, Cato in Sen. Ep. 94, 28: I do not deem it n. to write ..., (non) habeo n. scribere, Cic. Att. 10, 1, extr.: necesse est is also (less freq.) foll. by subj., Zumpt L. G. § 625: cf. Sall. Jug. 31, ad init., necesse est suomet ipsi more praecipites eant, i. e. all that is n. is that, etc. 3. ŏpus, indecl. (need, needful: either with abl. of thing needed; or as indecl. predicate, the thing needed being nom.): before you begin, deliberation is n., prius quam incipias, consulto opus est, Sall. Cat. 1, extr.: v. needful. II. Inevitable: nĕcessārius: if the first link in the chain (of cause and effect) is n., it follows ..., si, quod primum in connexo est, n. est, sequitur, etc., Cic. Fat. 7, 14, et pass.: a n. conclusion, n. conclusio, id. Top. 16, 60. Or expr. by necesse: v. necessarily.