Hiatus

Attic more than any other dialect disliked the immediate succession of two vowel sounds in adjoining syllables. To avoid such succession, which often arose in the formation and inflection of words, various means were employed: contraction (48 ff.), when the vowels collided in the middle of a word; or, when the succession occurred between two words (hiatus), by crasis (62 ff.), elision (70 ff.), aphaeresis (76), or by affixing a movable consonant at the end of the former word (134).

Hiatus is usually avoided in prose writers by elision (70 ff.); but in cases where elision is not possible, hiatus is allowed to remain by different writers in different degrees, commonly after short words, such as ὦ, εἰ, ἤ, καί, μή, and the forms of the article.