the former when use is made of a longer vowel than usual or a syllable inserted, and the latter when part of the word is curtailed.
An example of a lengthened word is πόληος for πολέως and Πηληιάδεω for Πηλείδου; and of a curtailed word κρῖ and δῶ, and e.g. μία γίνεται ἀμφοτέρων ὄψ. [Note]
A word is "altered" when the poet coins part of the word and leaves the rest unchanged, e.g. δεξιτερὸν κατὰ μαζόν instead of δεξιόν.
Of the nouns themselves, some are masculine, some feminine, and some neuter. [Note]
Masculine are all that end in N and P and Σ and in the two compounds of Σ, Ψ and Ξ.
Feminine are all that end in those of the vowels that are always long, for instance Η and Ω, and in Α among vowels that can be lengthened.
The result is that the number of masculine and feminine terminations is the same, for Ψ and Ξ are the same as Σ.
No noun ends in a mute or in a short vowel.
Only three end in Ι, μέλι, κόμμι, and πέπερι. Five end in Υ. The neuters end in these letters and in Ν and Σ.
The merit of diction is to be clear and not commonplace. The clearest diction is that made up of ordinary words, but it is commonplace.