diaeresis
di.aer.e.sis \di--'er-*-s*s\ \-'er-*-.se-z\ \.di--*-'ret-ik\ n or di.aer.e.ses [LL diaeresis, fr. Gk diairesis, fr. diairein to divide, fr.] pl dia- + hairein to take 1: the division of one syllable into two esp. by separating the vowel eleme nts of a diphthong or by resolving a w or y sound into a vowel 2: a mark : placed over a vowel to to indicate that the vowel is pron ounced in a separate syllable (as in naive, Bronte) 3: the break in a verse caused by the coincidence of the end of a foot with the end of a word - di.ae.ret.ic aj
Webster's English Dictionary