Diaeresis
Pronunciation : Di*?r"e*sis, Di*er"e*sis
Part of Speech : n.;
Etymology : [L. diaeresis, Gr. Heresy.]
Definition : 1. (Gram.)
Defn: The separation or resolution of one syllable into two; -- the opposite of syn?resis.
2. A mark consisting of two dots [..], placed over the second of two adjacent vowels, to denote that they are to be pronounced as distinct letters; as, co?perate, a?rial.
pl. Di?reses or Diereses.
Source : Webster's Unabridged Dictionary, 1913