Diaeretic

Adjective

1. Featuring diaeresis.

   "The word create is dieretic, whereas creature is synaeretic."

2. Written with a diaeresis.

   "Some words have many spellings: Take, for example, coordinate, which also has a hyphenated spelling variant — co-ordinate — and a dieretic one, coördinate."

3. Separative.