Diæresis /(?; 277)/

Di·ær·e·sis

Diæresis

n.

pl. Diæreses, Diereses

  1. The separation or resolution of one syllable into two; -- the opposite of synæresis. (Gram.)
  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, coöperate, aërial.