— dieretic /duy'euh ret"ik/ , adj.
/duy er"euh sis/ , n. , pl. diereses /-seez'/ .
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 .
[ 1605-15; diaeresis diaíresis lit., distinction, division, equiv. to diaire-, s. of diaireîn to divide ( di- DI- 3 + haireîn to take) + -sis -SIS ]