Synizesis

In poetry two vowels, or a vowel and a diphthong, belonging to successive syllables may unite to form a single syllable in pronunciation, but not in writing. Thus, βέλεα missiles, πόλεως city, Πηληϊάδεω son of Peleus, χρῡσέῳ golden. This is called Synizēsis (συνίζησις settling together).

Synizesis may occur between two words when the first ends in a long vowel or diphthong. This is especially the case with δή now, ἤ or, ἦ (interrog.), μή not, ἐπεί since, ἐγώ I, ὦ oh; as ἦ οὐ O 18.

a. The term synizesis is often restricted to cases where the first vowel is long. Where the first vowel is short, ε, ι were sounded nearly like y; υ nearly like ω. Cp. 44 a. The single syllable produced by synizesis is almost always long.