Discussion of accentuation rules for Greek disyllabic words ending in -ος, -υος, -οος, -εος and related forms, with place-name examples (Σάος, Ἴος, Χίος, Κῖος), notes on vowel/consonant influence and gender.
Τὰ εἰς 'ος' δισύλλαβα τὸ δίχρονον ἔχοντα βραχὺ βαρύνεται, σάος καὶ Σάος ἡ τῶν Σαΐων νῆσος. Ἴος νῆσος τῶν Κυκλάδων ἀπὸ Ἰώνων οἰκησάντων, ἔστι καὶ Λυδίας. Τίος πόλις Παφλαγονίας ἀπὸ Τιέως ἱερέως τὸ γένος Μιλησίου, ὡς Φίλων. Δημοσθένης δ´ ἐν Βιθυνιακοῖς φησι κτιστὴν τῆς πόλεως γενέσθαι Πάταρον ἑλόντα Παφλαγονίαν καὶ ἐκ τοῦ τιμᾶν τὸν Δία Τίον προσαγορεῦσαι. μέμνηται καὶ Μένιππος ἐν Παφλαγονίας περίπλῳ »ἀπὸ Ψύλλης χωρίου ἐς Τίον πόλιν καὶ ποταμὸν Βιλλαῖον στάδιοι ϟ« καὶ »οἱ πάντες ἀπὸ Ἡρακλείας ἐς Τίον πόλιν καὶ ποταμὸν Βιλλαῖον στάδιοι τοʹ«. καὶ πάλιν »οἱ πάντες ἀπὸ Τίου εἰς Ἄμαστριν στάδιοι σκʹ. Στράβων ἐν δωδεκάτῳ οὐδετέρως καὶ τρισυλλάβως τὸ Τίειόν φησιν. Χίος ἡ ἐπιφανεστάτη νῆσος τῶν Ἰώνων, ἔχουσα καὶ πόλιν ὁμώνυμον. Ἑκαταῖος Εὐρώπῃ «Χίος κατὰ Ἐρυθράς, ἐν δὲ πόλις Χίος». ἀπὸ Χίου τῆς Ὠκεανοῦ ἢ ἀπὸ τῆς χιόνος τῆς ἐκεῖ γενομένης πολλῆς ἢ ἀπὸ νύμφης τῆς Χιόνης. ἔστι καὶ ἑτέρα πόλις Καρίας Χίος κατὰ Τριόπιον κειμένη ἐν τῇ χερρονήσῳ. καὶ γʹ ἐν Εὐβοίᾳ. Κίος ποταμὸς καὶ πόλις Βιθυνίας, Δρίος τὸ Φρίκειον ὄρος, ἴος ὁ μόνος, βίος ἡ ζωή, βιός δὲ τὸ τόξον. σεσημείωται τὸ μνιός ὁ ἁπαλός παρ´ Εὐφορίωνι. Τὰ διὰ τοῦ 'υος' δισύλλαβα ἀρσενικὰ βαρύνεται, Δρῦος ὄνομα κύριον υἱὸς Αἰγύπτου καὶ Φλῦος. σεσημείωται ὁ πυός ὀξυτόνως καὶ ἀρσενικῶς. τὸ δὲ νυός ἡ νύμφη θηλυκὸν ὀξύνεται. Τὰ διὰ τοῦ 'οος' καὶ 'εος' δισύλλαβα ἀπὸ συμφώνου ἀρχόμενα καὶ μὴ μόνου τοῦ 'θ' βαρύνεται, νόος, γόος, ῥόος, πλόος, θρόος, φλόος, κόος, ὃ λέγεται καὶ κῶος, καὶ Κόος ὄνομα τόπου, χνόος, φλέος, Κέος, Τέος, πλέος, νέος, διὸ καὶ τὸ ζόος παρ´ Ἐπιχάρμῳ οἱ πλείους ἐβάρυναν «τρὶς ἀπεδόθη ζόος». ὁμοίως καὶ τὸ σόος τὸ κύριον καὶ τὸ προσηγορικόν, ὅπερ ἡ συνήθεια διὰ τοῦ 'ω' γράφει, τινὲς δὲ καὶ σὺν τῷ 'ι'. τὸ δὲ ἑός ὀξύνεται, ἀπὸ φωνήεντος γάρ. καὶ τὸ θοός καὶ θεός ὡς ἀπὸ τοῦ 'θ' μόνου.
The disyllables in -ος that have a long-and-short vowel are accented with a grave when the vowel is short: σάος, and Σάος, the island of the Saïans. Ἴος, an island of the Cyclades, from Ionians who settled it; there is also one in Lydia. Τίος, a city of Paphlagonia, from Τιεύς, a priest by descent, a Milesian, as Philo says. But Demosthenes in the Bithyniaca says that Patarus became founder of the city after taking Paphlagonia, and that from honoring Zeus he called it Τίον. Menippus too mentions it in the Periplus of Paphlagonia: “from the place Ψύλλη to the city Τίον and the river Βιλλαῖος, 90 stades,” and “the total from Heracleia to the city Τίον and the river Βιλλαῖος, 370 stades”; and again, “the total from Τίος to Amastris, 220 stades.” Strabo in book twelve says Τίειόν with a neutral accent and as a trisyllable. Χίος, the most famous island of the Ionians, also having a city of the same name. Hecataeus in the Europa: “Chios opposite Erythrae, and in it a city Chios.” It is named either from Chios, son of Oceanus, or from the snow (χιών) that fell there in great quantity, or from the nymph Chione. There is also another city of Caria, Chios, lying opposite Triopion on the peninsula; and a third in Euboea. Κίος, a river and a city of Bithynia; Δρίος, Mount Phriceion; ἴος, the single one; βίος, life; but βιός, the bow. The form μνιός, “the tender,” is noted in Euphorion. The masculine disyllables in -υος are accented with a grave: Δρῦος, a proper name, son of Aegyptus, and Φλῦος. πυός is noted as oxytone and masculine; but νυός, “the nymph,” feminine, is accented with an acute. The disyllables in -οος and -εος, beginning with a consonant and not only with θ, are accented with a grave: νόος, γόος, ῥόος, πλόος, θρόος, φλόος, κόος (also said κῶος), and Κόος as a place-name, χνόος, φλέος, Κέος, Τέος, πλέος, νέος; therefore most people also gave a grave accent to ζόος in Epicharmus: “thrice was ζόος restored.” Likewise σόος, both the proper name and the appellative, which usage writes with ω, though some also with ι. But ἑός is accented with an acute, since it begins with a vowel; and so too θοός and θεός, as beginning with θ alone.