Diaerisis ö

Signs of letters

• It is used to separate and mark of monographs (in which two vowels are pronounced separately)
  coöperation

• It can be used to show vocalic terminal e
  Brontë

This use of the diaeresis peaked in the late 19th and early 20th centuries, but it was never applied extensively across the language: only a handful of diaereses, including coöperation and Brontë, are encountered with any appreciable frequency in English; thus reëxamine, reïterate, deëmphasize, etc. are seldom encountered. In borrowings from Modern French, whose orthography utilizes the diaeresis as a means to differentiate graphemes, various English dictionaries list the dieresis as optional (as in naive and naïve) despite the juxtaposition of a and i