Morphological and accentual rules for Attic plural forms: how different plural endings (‘-αι’, ‘-αις’? actually Greek endings like -αι, -ες, -ους, -ω, -ι, -α, -η) affect accent placement; examples showing shifts (oxytone, perispomenon, circumflex) and treatments by Athenians (contraction with eta, etc.).
τὸ μονογενές. Ἐὰν δὲ μὴ ὦσιν ἀπὸ τῶν εἰς 'ος', τοῖς ἑνικοῖς ἑαυτῶν ἀκολουθοῦσι κατὰ τὸν τόνον οἷον Θρῇσσα Θρῇσσαι, θῆσσα θῆσσαι ἡ μισθῷ δουλεύουσα, τύπτουσα τύπτουσαι, χαρίεσσα χαρίεσσαι, τετυφυῖα τετυφυῖαι, ταχεῖα ταχεῖαι, βραδεῖα βραδεῖαι, μέλαινα μέλαιναι. τὸ δὲ Τρῳαί καὶ δμῳαί ὀξυνόμενα ὁμολογοῦσι πεπτωκέναι ἀπὸ ὀξυτόνου ἑνικοῦ Τρῳή καὶ δμῳή. Αἱ εἰς 'εις' ἀπὸ μὲν βαρυτόνων ἑνικῶν βαρύνονται, Δημοσθένης Δημοσθένεις, ἀπὸ δὲ τῶν ὀξυνομένων ἢ περισπωμένων περισπῶνται, εὐγενής εὐγενεῖς, Ἡρακλῆς Ἡρακλεῖς. τῶν δὲ τοιούτων Ἀθηναῖοι τὴν συναίρεσιν ποιοῦνται διὰ τοῦ 'η' καὶ ὁμοίως περισπῶσιν, ἱππῆς ἐκ τοῦ ἱππέες, βασιλέες βασιλῆς. Οἱ ἥρωες ἡ εὐθεῖα τῶν πληθυντικῶν εὕρηται κατὰ κρᾶσιν παρὰ Ἀριστοφάνει ἐν Ἥρωσιν «οἱ γὰρ ἥρως ἐγγύς εἰσιν» ἀντὶ τοῦ ἥρωες. Αἱ εἰς 'ους' ἀπὸ συγκριτικῶν ἐνδείᾳ τοῦ 'ν' καὶ κράσει τῶν φωνηέντων γενόμενα παροξύνονται οἷον μείζονες μείζους, βελτίονες βελτίους καὶ τὰ ὅμοια. Τὰ Ἀττικὰ εἰς 'ω' καὶ εἰς 'ι' λήγοντα κατὰ τὴν εὐθεῖαν τῶν πληθυντικῶν ὁμοτονοῦσι τῇ εὐθείᾳ τῶν ἑνικῶν οἷον ὁ εὔγεως οἱ εὔγεῳ, ὁ Μενέλεως οἱ Μενέλεῳ, ὁ νεώς οἱ νεῴ, ὁ λεώς οἱ λεῴ. Πᾶσα εὐθεῖα πληθυντικὴ οὐδετέρου ὀνόματος ἐντελὴς εἰς 'α' λήγει καὶ ἐπὶ τῆς αὐτῆς συλλαβῆς ἔχει τὸν τόνον, ἐφ´ ἧς καὶ ἡ ἑνικὴ εὐθεῖα, γράμμα γράμματα, φίλον φίλα, καλόν καλά· κάνεον μὲν κάνεα προπαροξυτόνως, κανοῦν δὲ κανᾶ προπερισπωμένως διὰ τὴν συναίρεσιν. αἱ δὲ εἰς 'η' ἐκ συναιρέσεώς εἰσι καὶ πρὸς τὴν συναίρεσιν τὸν τόνον ποιοῦνται, τείχεα τείχη· αἱ γὰρ δύο βαρεῖαι εἰς βαρεῖαν συναιροῦνται. τὰ εὐσεβέα δὲ τὰ εὐσεβῆ· ἡ γὰρ ὀξεῖα καὶ βαρεῖα εἰς περισπωμένην συναιρεῖται. {1Περὶ τόνου τῆς πληθυντικῆς γενικῆς.}1 Αἱ γενικαὶ αἵτε ἑνικαὶ καὶ πληθυντικαὶ ἀπὸ μὲν τῶν ὀξυτόνων ἢ περισπωμένων ὀνομάτων, εἰ μὲν ἰσοσυλλάβως κλίνοιντο, πάντως περισπῶνται,
The monogenēs. But if they are not derived from those in -ος, they follow their own singulars in respect of accent, as Θρῇσσα Θρῇσσαι, θῆσσα θῆσσαι, she who serves for hire, τύπτουσα τύπτουσαι, χαρίεσσα χαρίεσσαι, τετυφυῖα τετυφυῖαι, ταχεῖα ταχεῖαι, βραδεῖα βραδεῖαι, μέλαινα μέλαιναι. But Τρῳαί and δμῳαί, being accented on the last syllable, agree that they have fallen from an oxytone singular Τρῳή and δμῳή. Those in -εις, from barytone singulars are barytone, Δημοσθένης Δημοσθένεις, but from those accented on the last syllable or circumflexed they are circumflexed, εὐγενής εὐγενεῖς, Ἡρακλῆς Ἡρακλεῖς. Of such forms the Athenians make the contraction through η and likewise circumflex, ἱππῆς from ἱππέες, βασιλέες βασιλῆς. In the case of ἥρωες, the nominative plural is found by crasis in Aristophanes in Heroes: «οἱ γὰρ ἥρως ἐγγύς εἰσιν» instead of ἥρωες. Those in -ους, formed from comparatives by loss of ν and by crasis of the vowels, are accented on the penult, as μείζονες μείζους, βελτίονες βελτίους, and the like. The Attic forms ending in -ω and in -ι in the nominative plural have the same accent as the nominative singular, as ὁ εὔγεως οἱ εὔγεῳ, ὁ Μενέλεως οἱ Μενέλεῳ, ὁ νεώς οἱ νεῴ, ὁ λεώς οἱ λεῴ. Every complete nominative plural of a neuter noun ends in -α and has the accent on the same syllable as the nominative singular, γράμμα γράμματα, φίλον φίλα, καλόν καλά; κάνεον indeed κάνεα with antepenult accent, but κανοῦν κανᾶ with circumflex on the prepenult because of the contraction. Those in -η are from contraction and place the accent in accordance with the contraction, τείχεα τείχη; for two graves are contracted into a grave. But τὰ εὐσεβέα becomes τὰ εὐσεβῆ; for an acute and a grave are contracted into a circumflex. {1On the accent of the plural genitive.}1 The genitives, both singular and plural, from oxytone or circumflexed nouns—if they are declined with the same number of syllables—are in every case circumflexed,