NECESSARY Copy link • NECESSARY 1. (With a substantive), necessarius: a necessary thing, necessitas, res necessaria. (Without a substantive) it is necessary, opus est (there is need of: ☞ the person who has need of a thing is in the dative; the thing needed in the nominative or ablative; also, with an infinitive, which is then the casus subjecti; the genitive occurs twice in Livy, 22, 51; 23, 21, and sometimes, but very rarely, in the poets; Vid: Ramsh., §142; Zumpt, §464; Krebs, §392; Wyttenb., §255, 314, 324): necesse est; necessarium est, oportet [Vid: MUST]: usus est (☞ almost only in the poets; once in Livy, rarely in Caes., ; Vid: Ramsh., § 142, 2, n. 3; Zumpt, §464, 2; Herzog, ad Caes., B.G., 4, 2): also by attinet; e.g., it is not necessary to say, nihil attinet dicere: it is not necessary that you should wait, nihil opus est, exspectare te (Cic.): it is not necessary, nihil est, non est quod (☞ not non opus est quod): to consider necessary, necesse habere: I thought it necessary to do, etc., hoc faciendum putavi: not to find anything necessary, supersedere posse aliqua re; or with an infinitive; e.g., loqui apud vos supersedissem (Liv.). ☞ Avoid the Grecism, opus habere; which occurs only once, Col., 9, 1, 5. 2. s. res necessaria: necessitas: necessaries, res quibus homines utuntur; res quibus carere non possumus; ea quae natura desiderat: necessaries of life, res ad vitam necessariae; usus vitae necessarii: quae sunt ad vivendum necessaria; quae ad victum cultumque pertinent.