Pronunciation: (dī-er'u-sis),[key] —n., —pl.-sesPronunciation: (-sēz").[key] 1. the separation of two adjacent vowels, dividing one syllable into two.
2. a sign (¨) placed over the second of two adjacent vowels to indicate separate pronunciation, as in one spelling of the older forms naïve and coöperate: no longer widely used in English.
3. Pros.the division made in a line or verse by coincidence of the end of a foot and the end of a word. Also,diaeresis.