After αν, ον, αρ, ορ, ι̯ is shifted to the preceding syllable, forming αιν, οιν, αιρ, οιρ. This is called Epenthesis (ἐπένθεσις insertion).
φαίνω show for φαν-ι̯ω, μέλαινα black for μελαν-ι̯α, σπαίρω gasp for σπαρ-ι̯ω, μοῖρα fate for μορ-ι̯α. (So κλαίω weep for κλαϝ-ι̯ω 38 a.) On ι after εν, ερ, ιν, ιρ, υν, υρ, see 37 a.