crasis

crasis, in classical Greek, the contraction of two vowels or diphthongs at the end of one word and the beginning of an immediately following word, as kán for kaì án or houmós for ho emós. Crasis is especially common in some lyric poetry and in Old Comedy. The term sometimes refers to word-internal contraction in Latin, as nīl from nihil. The word is from the Greek krâsis, literally, “mixing or blending.”