used in direct negation not, Lat. non.
A.USAGE:
I.adhering to single words so as to form a quasi-compd. with them, οὐ δίδωμι to withhold, οὐκ ἐῶ to refuse, οὐκ ἐθέλω nolo, οὔ φημι nego.
2.in dependent clauses οὐ is used,
b.in Causal sentences, and in Temporal sentences that involve special times, ἄχθεται ὅτι οὐ κάρτα θεραπεύεται Hdt.; οὐκ ἔσθ᾽ ἐραστὴς ὅστις οὐκ ἀεὶ φιλεῖ Eur.
3.in a conditional clause μή is necessary, except,
b.when the subjoined clause is hypothetical in form only, μὴ θαυμάσῃς, εἰ πολλὰ οὐ πρέπει σοι (where εἰ = ὅ τι) Isocr.; δεινὸν γὰρ ἂν εἴη πρῆγμα, εἰ Ἕλληνας οὐ τιμωρησόμεθα Hdt.
4.οὐ is used with Inf. in oratio obl., when it represents the Ind. of oratio recta, λέγοντες οὐκ εἶναι αὐτόνομοι Thuc.; οἶμαι οὐκ ὀλίγον ἔργον αὐτὸ εἶναι Plat.
5.οὐ is used with the Participle, when it can be resolved into a finite sentence with οὐ; κατενόησαν οὐ πολλοὺς τοὺς Θηβαίους ὄντας ῀ ὅ τι οὐ πολλοί εἰσι, Thuc.
6.Adjectives and abstract Substantives with the Article commonly take μή (v. μή B. 6), but οὐ is occasionally used, τῶν γεφυρῶν οὐ διάλυσιν the nondissolution of the bridge, the fact of its not being broken up, Thuc.; so, ἡ οὐ περιτείχισις id=Thuc.
B.ACCUMULATION: the negative is often repeated, so that two negatives do not make an affirmative, attic, οὐκ ἔστιν οὐδὲν κρεῖσσον φίλου Eur.; καθεύδων οὐδεὶς οὐδενὸς ἄξιος οὐδὲν μᾶλλον τοῦ μὴ ζῶντος Plat.; οὐδενὶ οὐδαμῆ οὐδαμῶς οὐδεμίαν κοινωνίαν ἔχει id=Plat.
C.PLEONASM OF οὐ: after Verbs of denying, doubting, and disputing, followed by ὡς or ὅτι, οὐ is inserted, where in Engl. the negat. is not required, ἀμφισβητεῖ ὡς οὐ δεῖ δίκην διδόναι Plat. Like this is the appearance of οὐ in the second member of a negative comparative sentence, ἥκει ὁ Πέρσης οὐδέν τι μᾶλλον ἐπ᾽ ἡμέας ἢ οὐ καὶ ἐπ᾽ ὑμέας Hdt.