Greek accentuation rules: placement of acute, grave, circumflex; oxytone, paroxytone, proparoxytone, perispomenon, barytone; examples and exceptions (Il.13.1, Menelaos, Oedipus, Melampus).
εἰ δὲ εὐκτικόν, παροξύνεται· ὅτε δέ ἐστι τὸ ποίησαι προστακτικῆς μέσης ἀόριστος πρῶτος, προπαροξύνεται. Πᾶσα ὀξεῖα ἐπὶ τέλους λέξεως οὖσα, εἰ μὴ ἐπιφέροιτο μετ´ αὐτὴν στιγμή, πάντως ἐν τῇ συμφράσει κοιμίζεται εἰς βαρεῖαν οἷον «Ζεὺς δ´ ἐπεὶ οὖν Τρῶάς τε καὶ Ἕκτορα» (Il. 13, 1) τό τε Ζεὺς καὶ ἐπὶ βαρύνεται, ὅτι στιγμὴ μετὰ ταῦτα οὐ τίθεται. Ἰστέον δὲ ὅτι καθ´ ἑκάστην λέξιν ἐν μιᾷ συλλαβῇ τίθεμεν ἢ ὀξεῖαν ἢ περισπωμένην, ἐν δὲ ταῖς λοιπαῖς συλλαβαῖς βαρεῖαν· οἷον ἐν τῷ Μὲνέλὰὸς δευτέρα συλλαβὴ ὀξύνεται, αἱ δὲ λοιπαὶ βαρύνονται, καὶ ἐν τῷ ἂλλοῖὸς ἡ μέση περισπᾶται, ἡ δὲ πρώτη καὶ τρίτη βαρύνονται· διὸ καὶ βαρύτονα καλεῖται τὰ παροξύτονα καὶ προπαροξύτονα καὶ προπερισπώμενα, διὸ ἡ τελευταία τούτων βαρύνεται· ἀλλ´ ὡς ὁμολογουμένας τὰς τοιαύτας βαρείας ἐῶμεν, διὰ τὸ μὴ καταστίζειν τὰ βιβλία. Ἡ ὀξεῖα οὖν καὶ ἡ βαρεῖα περισπωμένην ποιοῦσιν οἷον φάὸς φῶς, εὐγενέὸς εὐγενοῦς. ἀνάπαλιν δὲ ἡ βαρεῖα καὶ ὀξεῖα εἰς ὀξεῖαν συναιροῦνται, εἰ μὴ τονικὸν κωλύσῃ παράγγελμα, οἷον ζὼός ζώς, Πρὸΐτου Προίτου, κὸΐλου κοίλου· τὸ γὰρ κόϊλος κοῖλος διὰ τονικὸν παράγγελμα περιεσπάσθη. τὸ δὲ ἀδελφιδὲός ἀδελφιδοῦς καὶ τὰ ὅμοια δι´ ἕτερον λόγον περιεσπάσθη· τὰ γὰρ εἰς 'ους' ἁπλᾶ πάντα περισπᾶται οἷον βοῦς, χοῦς, πλοῦς. τὰ δὲ σύνθετα βαρύνεται οἷον Μελάμπους, Οἰδίπους, ὅθεν σημειούμεθα τὸ πούς καὶ ὀδούς παραλόγως
If it is optative, it is accented on the penult; but when it is ποίησαι, the first aorist middle imperative, it is accented on the antepenult. Every acute that stands on the final syllable of a word, if no punctuation follows immediately after it, is in any case in the phrase lowered to a grave, as in “Ζεὺς δ´ ἐπεὶ οὖν Τρῶάς τε καὶ Ἕκτορα” (Il. 13, 1): both Ζεὺς and δ´ are also pronounced with a grave, because no punctuation is placed after them. One must know that in each word we place either an acute or a circumflex on one syllable, and on the remaining syllables a grave; for example, in Μὲνέλὰὸς the second syllable is accented with an acute, while the rest are pronounced with a grave; and in ἂλλοῖὸς the middle syllable has a circumflex, while the first and third are pronounced with a grave. For this reason the paroxytone, proparoxytone, and properispomenon words are also called barytone, because the final syllable of these is pronounced with a grave; but we let such graves pass as agreed upon, because the books are not punctuated. The acute, then, and the grave make a circumflex, as φάὸς → φῶς, εὐγενέὸς → εὐγενοῦς. Conversely, the grave and the acute contract into an acute, unless a tonal rule prevents it, as ζὼός → ζώς, Πρὸΐτου → Προίτου, κὸΐλου → κοίλου; for κόϊλος → κοῖλος was circumflexed because of a tonal rule. But ἀδελφιδὲός → ἀδελφιδοῦς and the like were circumflexed for another reason: for all simple words ending in -ους are circumflexed, as βοῦς, χοῦς, πλοῦς; but the compounds are pronounced with a grave, as Μελάμπους, Οἰδίπους, whence we note that πούς and ὀδούς are anomalous.