Phonological rules: the vowel ο is 'psilosed' (loss of roughness) before consonants like ν, π (except when λ intervenes), ρ (with some exceptions) and τ; many examples given (ὄνυξ, ὄνομα, ὀπίσω, ὄρος, ὄτλος). υ is generally dasynated at word-initial position except in Aeolic forms and before ζ/ξ/ψ not found; αυ diphthong is psilosed; many exceptions and morphological notes included.
Τὸ 'ο' πρὸ τοῦ 'ν' ἐν ταῖς ὑπὲρ μίαν συλλαβὴν λέξεσι ψιλοῦται, ὄνυξ, ὄναρ, ὄνομα. Τὸ 'ο' πρὸ τοῦ 'π' ψιλοῦται, εἰ μὴ τὸ 'λ' ἐπάγοιτο, ὀπίσω, ὀπιπεύω, ὀπή, ὀπώρα· παρὰ τὸ ἕπω δασυνόμενον ψιλούμενον ἐγένετο ὀπάων. οὕτως ἔχει καὶ τὸ ὄπατρος· οὐκ ἔστι δὲ ψιλωτέον ὡς οἴονται διὰ τὴν συγκοπήν. πολλὰ γάρ φασι διὰ τὴν συγκοπὴν ψιλοῦσθαι. ἀλλὰ καὶ δασύνεται, ἑστήκαμεν ἕσταμεν, Ἡράκλεες Ἥρακλες. πρόσκειται «εἰ μὴ τὸ 'λ' ἐπάγοιτο» διὰ τὸ ὁπλή καὶ ὅπλον καὶ τὰ ἀπὸ τούτων παρηγμένα. τὸ δὲ ὁπόσος, ὁποῖος, ὅπως καὶ τὰ ὅμοια ὡς ἀναφορικὰ δασύνεται. Τὸ 'ο' ἐπιφερομένου τοῦ 'ρ' ψιλοῦται, ὄρος τὸ οὐδέτερον, ὄρυζα, ὀρεύς, ὀρέγω, Ὀρέστης, πλὴν τοῦ ὁρῶ ὁρᾷς καὶ ὅρος ἀρσενικὸν ὅπερ ἀπὸ τοῦ ὁρῶ τὸ βλέπω γέγονεν. καὶ γὰρ ὁ ὅρος εὐόρατα καὶ εὔοπτα ποιεῖ ἡμῖν τὰ ὁριζόμενα. καὶ ὁρίζω καὶ ὅρκος ἐκ τοῦ ὅρος. καὶ γὰρ οἱ ὀμνύοντες ὁρίζονται καὶ ὀμνύουσιν. Τὸ 'ο' πρὸ τοῦ 'τ' ψιλοῦται, ὀτρηρός, ὀτοτύζειν, ὄτλος. οὐ μάχεται τὸ ὅτε καὶ ὅτι δασυνόμενα. Τὸ 'υ' πάσης λέξεως ἄρχον δασύνεται πλὴν τῶν Αἰολικῶν. τὸ ὐββάλλειν ψιλωτέον. ἔστι γὰρ Αἰολικόν. καὶ ὔμμες ψιλωτέον· ἡ γὰρ λέξις Αἰολική. τὸ 'υ' καθαρὸν ἐν ἀρχῇ λέξεως παρὰ τοῖς Ἕλλησιν πρὸ τοῦ 'χ' ἀπείρηται. καθαρὸν δὲ εἶπον, ἐπεὶ τὸ ὔρχα οὐ καθαρὸν ἔχον τὸ 'υ' εὕρηται. πρὸ τοῦ 'ζ' ἢ 'ξ' ἢ 'ψ' τὸ 'υ' οὐχ εὕρηται, εἰ μὴ ἐν τῷ ὕψος. γεγονέναι δὲ καὶ αὐτό φασι παρὰ τὸ ὄπτω τὸ βλέπω, ὄψω ὄψος καὶ τροπῇ Αἰολικῇ ὕψος. Ἡ 'αυ' δίφθογγος ψιλοῦται, αὔξω, αὐδῶ, αὐτός, αὔριον, πλὴν τοῦ αὕτη βαρύτονον ἀπὸ τοῦ οὗτος καὶ αὑτόν ἀντὶ τοῦ ἑαυτόν. τὸ
The ‘ο’ before ‘ν’ in words of more than one syllable is without rough breathing: ὄνυξ, ὄναρ, ὄνομα. The ‘ο’ before ‘π’ is without rough breathing, unless ‘λ’ follows: ὀπίσω, ὀπιπεύω, ὀπή, ὀπώρα; from ἕπω, which has rough breathing, when it lost the rough breathing there arose ὀπάων. So too is ὄπατρος; but it is not to be given smooth breathing, as they think, because of syncope. For they say that many words are given smooth breathing because of syncope. But words also take rough breathing: ἑστήκαμεν, ἕσταμεν; Ἡράκλεες, Ἥρακλες. The clause “unless ‘λ’ follows” is added because of ὁπλή and ὅπλον and the derivatives formed from these. But ὁπόσος, ὁποῖος, ὅπως and the like, as relative forms, take rough breathing. The ‘ο’ when ‘ρ’ follows is without rough breathing: ὄρος (the neuter), ὄρυζα, ὀρεύς, ὀρέγω, Ὀρέστης, except ὁρῶ, ὁρᾷς, and ὅρος (masculine), which has arisen from ὁρῶ in the sense ‘I see’. For the ὅρος makes the things delimited by it clearly visible and easy to see for us. And ὁρίζω and ὅρκος are from ὅρος; for those who swear set bounds and swear. The ‘ο’ before ‘τ’ is without rough breathing: ὀτρηρός, ὀτοτύζειν, ὄτλος. ὅτε and ὅτι, which take rough breathing, are not in conflict with this. ‘υ’ at the beginning of every word takes rough breathing, except in Aeolic forms. ὐββάλλειν is to be given smooth breathing, for it is Aeolic; and ὔμμες is to be given smooth breathing, for the word is Aeolic. A pure initial ‘υ’ among the Greeks before ‘χ’ is not found. I said “pure” because ὔρχα has been found with ‘υ’ not pure. Before ‘ζ’ or ‘ξ’ or ‘ψ’ ‘υ’ has not been found, except in ὕψος. And they say that this too has come from ὄπτω in the sense ‘I see’: ὄψω, ὄψος, and by an Aeolic change ὕψος. The diphthong ‘αυ’ is without rough breathing: αὔξω, αὐδῶ, αὐτός, αὔριον, except αὕτη with barytone accent, from οὗτος, and αὑτόν in place of ἑαυτόν. The