[di.aer.e.sis] n, pl -e.ses [LL diaeresis, fr. Gk diairesis, lit., division, fr. diairein to divide, fr. dia- + hairein to take] (ca. 1611) 1: a mark in the form of two dots placed over a vowel to indicate that the vowel is pronounced in a separate syllable
2: 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 adj