A diacritical mark (¨) placed over a vowel to indicate that it is pronounced in a separate syllable. In the word 'naïve', the dieresis over the 'i' indicates that it is pronounced in a separate syllable.
The division of two adjacent vowels into separate syllables, especially the separation of a diphthong into its constituent vowel sounds. Some poets employ dieresis to pronounce "cooperate" as four distinct syllables.
Prosody: a break in a line of verse in which the end of a metrical foot coincides with the end of a word. The hexameter line shows a clear dieresis after the fourth foot.