[*] 411. Opus and ūsus , signifying need, take the Ablative:—1
- magistrātibus opus est (Leg. 3.5), there is need of magistrates.
- “nunc vīribus ūsus ” (Aen. 8.441) , now there is need of strength.
[*] Note.--The ablative with ūsus is not common in classic prose.
[*] a. With opus the ablative of a perfect participle is often found, either agreeing with a noun or used as a neuter abstract noun:—- opus est tuā exprōmptā malitiā atque astūtiā; (Ter. And. 723), I must have your best cunning and cleverness set to work.
- properātō opus erat (cf. Mil. 49), there was need of haste.
[*] Note 1.--So rarely with ūsus in comedy: as,quid istīs ūsust cōnscrīptīs (Pl. Bacch. 749), what's the good of having them in writing?
[*] Note 2.--The omission of the noun gives rise to complex constructions: as,quid opus factōst (cf. B. G. 1.42), what must be done? [Cf. quid opus est fierī ? with quō factō opus est ?]
[*] b. Opus is often found in the predicate, with the thing needed in the nominative as subject:—- “ dux nōbīs et auctor opus est ” (Fam. 2.6.4) , we need a chief and responsible adviser (a chief, etc., is necessary for us).
- “sī quid ipsī opus esset ” (B. G. 1.34) , if he himself wanted anything (if anything should be necessary for him).
- “ quae opus sunt ” (Cato R. R. 14.3) , things which are required.