Greek prosody: rules for accentuation when a word ends in a short syllable; behavior of αι and οι in final position; paroxytone forms (ναίχι, εἴθε, αἴθε), examples (οἶκος, ἦθος, ὦμος, Μήδειαι, ἄνθρωποι, μοῦσαι, κοῦροι), effects of following consonant and enclitic vs. consonant influences on tone.
βραχείας ληκτικῆς ἐφ´ ἑαυτῆς ἔχουσα τὸν τόνον περισπᾶται, οἶκος, ἦθος, ὦμος· χωρὶς τῶν διὰ τοῦ 'ι' ἢ 'θε' ἐπεκτεταμένων· ταῦτα γὰρ φυλάττει τὸν τόνον, ἅτε δὴ περιττῆς οὔσης τῆς συλλαβῆς. παροξύνεται γοῦν τὸ ναίχι καὶ εἴθε καὶ αἴθε. ἔνθεν σημειούμεθα τὸ οὐχί ὀξυνόμενον· τὸ δὲ ᾗχι προπερισπᾶται «ᾗχι ῥοὰς Σιμόεις συμβάλλετον ἠδὲ Σκάμανδρος» (Ε 774). Ἡ 'αι' καὶ 'οι' ἐν τέλει λέξεων κείμεναι, μὴ ἐπιφερομένου συμφώνου, ἐπὶ μὲν τῶν ἄλλων πάντων ἀντὶ βραχείας παραλαμβάνονται, ἐπὶ μέντοι τῶν εὐκτικῶν καὶ τῶν ἐπιῤῥημάτων ἀντὶ μακρᾶς· οἷον τοῦ μὲν πρώτου τὸ Μήδειαι καὶ ἄνθρωποι προπαροξύνονται· ἔτι δὲ καὶ τὸ μοῦσαι καὶ κοῦροι προπερισπᾶται, ὡς τῶν τελευταίων συλλαβῶν βραχειῶν οὐσῶν. εἰ δὲ σύμφωνον ἐπιφέρεται, μακραὶ γίνονται, ὅθεν τοῖς Ὁμήροις καὶ ταῖς Μηδείαις ὁ τόνος καταβιβάζεται καὶ πρὸ μιᾶς τοῦ τέλους ὀξὺς δίδοται· ὁμοίως καὶ ἐπὶ ταῖς μούσαις καὶ κούροις. τὸ μέντοι οἴκοι τοπικὸν ἐπίῤῥημα καὶ οἴμοι σχετλιαστικὸν παροξύνονται· καίτοι, ὅτε ἐστὶν ὄνομα τὸ οἶκοι, προπερισπᾶται. ἀλλὰ καὶ τὸ ποιῆσαι καὶ κεῖραι, εἰ μὲν ἀπαρέμφατον εἴη, προπερισπᾶται·
A short final syllable, having the accent on itself, is circumflexed: οἶκος, ἦθος, ὦμος—except for those extended by means of ‘ι’ or ‘θε’; for these keep the accent, since the syllable is in fact extrametrical. Accordingly ναίχι and εἴθε and αἴθε are accented on the penult. Hence we note that οὐχί is accented with an acute; but ᾗχι is accented with a circumflex on the antepenult: «ᾗχι ῥοὰς Σιμόεις συμβάλλετον ἠδὲ Σκάμανδρος» (Ε 774). The diphthongs ‘αι’ and ‘οι’, when they stand at the end of words and no consonant follows, in all other cases are taken as equivalent to a short syllable, but in the optatives and in adverbs as equivalent to a long; for example, in the first class Μήδειαι and ἄνθρωποι are accented on the antepenult; and moreover μοῦσαι and κοῦροι are accented with a circumflex on the antepenult, since the final syllables are short. But if a consonant follows, they become long; hence in Ὁμήροις and Μηδείαις the accent is lowered and an acute is given one syllable before the end; likewise also in μούσαις and κούροις. The local adverb οἴκοι, however, and the exclamatory οἴμοι are accented on the penult; and yet, when οἶκοι is a noun, it is accented with a circumflex on the antepenult. And also ποιῆσαι and κεῖραι, if they are infinitives, are accented with a circumflex on the antepenult;