dieresis

noun

1. A diacritic ( ¨ ) placed over a vowel letter (especially the second of two consecutive ones) indicating that it is sounded separately, usually forming a distinct syllable, as in the English words naïve, Noël and Brontë, the French haïr and the Dutch ruïne.
2. Distraction; the separation of a vowel, often a diphthong, into two distinct syllables.
3. A natural break in rhythm when a word ends at the end of a metrical foot, in a line of verse.
4. Hiatus; the occurrence of separate vowel sounds in adjacent syllables without an intervening consonant.