ou

οὐ, before a vowel with smooth breathing οὐκ, before one with rough breathing οὐχ (but improperly οὐχ ἰδού, Ac 2:7, WH, mg.; cf. WH, Intr., § 409; M, Pr., 44, 244),

[in LXX for לֹא, אַיִן, אֵין;]

neg. particle,

G. Abbott-Smith, A Manual Greek Lexicon of the New Testament, 1922 — public domain. References open in the reader.

οὐ,
the negative of fact and statement, as μή of will and thought; οὐ denies, μή rejects; οὐ is absolute, μή relative; οὐ objective, μή subjective. —The same differences hold for all compounds of οὐ and μή, and some examples of οὐδέ and οὐδείς are included below.—As to the Form, see infr. G. USAGRefs 5th c.BC+
I as the negative of single words,
II as the negative of the sentence.
I οὐ adhering to single words so as to form a quasi-compound with them:—with Verbs: οὐ δίδωμι withhold, Refs 8th c.BC+; οὐκ εἰῶ prevent, Refs; οὐκ ἐθέλω refuse, Refs; οὔ φημι deny, Refs 4th c.BC+; but sometimes οὐ is retained, εἰ δ᾽ ἂν.. οὐκ ἐθέλωσιν Refs 8th c.BC+; ἐάντε.. οὐ (variant{μή}) φῆτε ἐάντε φῆτε Refs 8th c.BC+ —On the use of οὐ in contrasts, see below Refs 5th c.BC+
II as negativing the whole sentence,
II.1 οὐ is frequently used alone, sometimes with the ellipsis of a definite Verb, οὔκ (i.e. ἀποκερῇ), ἄν γε ἐμοὶ πείθῃ Refs 5th c.BC+: sometimes as negativing the preceding sentence, Refs 5th c.BC+ and the accusative; sometimes without μά, οὐ τὸν πάντων θεῶν θεὸν πρόμον Ἅλιον Refs 5th c.BC+
II.2 with indicative of statement, τὴν δ᾽ ἐγὼ οὐ λύσω Refs 8th c.BC+; οὐ φθίνει Κροίσου φιλόφρων ἀρετά Refs 8th c.BC+
II.3 with subjunctive in future sense, only in Epic dialect, οὐ γάρ τίς με βίῃ γε ἑκὼν ἀέκοντα δίηται Refs
II.4 with optative in potential sense (without ἄν or κεν), also Epic dialect, ὃ οὐ δύο γ᾽ ἄνδρε φέροιεν Refs
II.5 with optative and ἄν, κείνοισι δ᾽ ἂν οὔ τις.. μαχέοιτο Refs 5th c.BC+
II.6 in dependent clauses οὐ is used,
II.6.a with ὅτι or ὡς, after Verbs of saying, knowing, and showing, ἐκ μέν τοι ἐρέω.. ὡς ἐγὼ οὔ τι ἑκὼν κατερύκομαι Refs 8th c.BC+: so with indicative or optative and ἄν, ἀπελογοῦντο ὡς οὐκ ἄν ποτε οὕτω μωροὶ ἦσαν Refs 5th c.BC+ in such sentences, see at {μή} Refs 5th c.BC+
II.6.b in all causal sentences, and in temporal and Relat. sentences unless there is conditional or final meaning, χωσαμένη, ὅ οἱ οὔ τι θαλύσια.. ῥέξε Refs 8th c.BC+: in causal relative sentences, οἵτινές σε οὐχὶ ἐσώσαμεν Refs 5th c.BC+; especially in the combinations, οὐκ ἔστιν ὅστις οὐ.., as οὐκ ἔστ᾽ ἐραστὴς ὅστις οὐκ ἀεὶ φιλεῖ Refs 5th c.BC+; οὐδείς ἐστιν ὅστις οὐ.. Refs 5th c.BC+
II.6.c after ὥστε with indicative or optative with ἄν, ὥστ᾽ οὐ δυνατόν σ᾽ εἵργειν ἔσται Refs 5th c.BC+infinitive is almost invariably due to indirect speech, ὥστ᾽ οὐκ αἰσχύνεσθαι (for οὐκ αἰσχύνονται) Refs 5th c.BC+—Rarely not in indirect speech, Refs 5th c.BC+
II.7 in a conditional clause μή is necessary, except,
II.7.a in Refs 8th c.BC+ clause precedes the apodosis and the verb is indicative, εἰ δέ μοι οὐκ ἐπέεσσ᾽ ἐπιπείσεται Refs 8th c.BC+
II.7.b when the εἰ clause is really causal, as after Verbs expressing surprise or emotion, μὴ θαυμάσῃς, εἰ πολλὰ τῶν εἰρημένων οὐ πρέπει σοι Refs 5th c.BC+
II.7.c when οὐ belongs closely to the next word (see. Refs 4th c.BC+, or is quoted unchanged, εἰ, ὡς νῦν φήσει, οὐ παρεσκευάσατο Refs 4th c.BC+; εἰ δ᾽ οὐκέτ᾽ ἐστί (i.e. ὥσπερ λέγεις), τίνι τρόπῳ διεφθάρη ; Refs 5th c.BC+
II.8 οὐ is used with infinitive in indirect speech, when it represents the indicative of orat. recta, φαμὲν δέ οἱ οὐ τελέεσθαι Refs 8th c.BC+; sometimes we have οὐ and μή in consecutive clauses, οἶμαι σοῦ κάκιον οὐδὲν ἂν τούτων κρατύνειν μηδ᾽ ἐπιθύνειν χερί Refs 5th c.BC+
II.9 οὐ is used with the participle, when it can be resolved into a finite sentence with οὐ, as after Verbs of knowing and showing, τὸν κατθανόνθ᾽ ὁρῶντες οὐ τιμώμενον Refs 5th c.BC+; or into a causal sentence, τῶν βαρβάρων οἱ πολλοὶ ἐν τῇ θαλάσσῃ διεφθάρησαν νέειν οὐκ ἐπιστάμενοι Refs 5th c.BC+; or into a concessive sentence, δόξω γυναῖκα καίπερ οὐκ ἔχων ἔχειν Refs 5th c.BC+ and participle, ὡς οὐχὶ συνδράσουσα νουθετεῖς τάδε Refs 5th c.BC+:—for exceptions, see at {μή} Refs 5th c.BC+
II.9.b when the participle is used with the Article, μή is generally used, unless there is a distinct reference to a fact, when οὐ is occasionally found, ἡμεῖς δὲ ἀπὸ τῆς οὐκ οὔσης ἔτι [πόλεως] ὁρμώμενοι Refs 5th c.BC+
II.10 Adjectives and abstract Substantives with the article commonly take μή (see. μή Refs 5th c.BC+ is occasionally used, τὰς οὐκ ἀναγκαίας πόσεις Refs 5th c.BC+; τὴν τῶν γεφυρῶν οὐ διάλυσιν the non- dissolution of the bridges, the fact of their notbeing broken up, Refs 5th c.BC+; so without the article, ἐν οὐ καιπῷ Refs
II.11 for οὐ μή, see entry
II.12 in questions οὐ ordinarily expects a positive answer, οὔ νυ καὶ ἄλλοι ἔασι..; Refs 8th c.BC+; οὐχ ὁράᾳς..; dost thou not see? NT+8th c.BC+: the diphthong is genuine and always written ου (ουκ, ουδε, etc.) in early Inscrr., Refs 4th c.BC+; οὐ abbreviated ο, Suid. see at {Φιλοξένου γραμμάτιον}.
H ACCENTUATION. οὐ is oxytone accusative to Hdn.Gr.1.494 (text doubtfulin 504): Refs 8th c.BC+
H.I οὐ in connexion with other Particles will be found in alphabetical order, οὐ γάρ, οὐ μή, etc.—The corresponding forms of μή should be compared.

H. G. Liddell, R. Scott, H. S. Jones, A Greek-English Lexicon (9th ed., 1925–1940) — digitised by the Perseus Digital Library and corrected and expanded by Tyndale House, Cambridge, via STEPBible-Data's TFLSJ table, CC BY 4.0. Covers all of Greek literature, not just the Bible.