di·er·e·sis or di·aer·e·sis (dī-ĕrĭ-sĭs)
n. pl. di·er·e·ses (-sēz′) or di·aer·e·ses
a. A mark (¨) placed over the second of two adjacent vowels to indicate that they are to be pronounced as separate sounds rather than a diphthong, as in naïve.
b. A mark (¨) placed over a vowel, such as the final vowel in Brontë, to indicate that the vowel is not silent.
2. A break or pause in a line of verse that occurs when the end of a word and the end of a metrical foot coincide.
[Late Latin diaeresis, from Greek diairesis, from diairein, to divide : dia-, apart; see DIA- + hairein, to take.]
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Indo-European & Semitic Roots Appendices
Thousands of entries in the dictionary include etymologies that trace their origins back to reconstructed proto-languages. You can obtain more information about these forms in our online appendices:
The Indo-European appendix covers nearly half of the Indo-European roots that have left their mark on English words. A more complete treatment of Indo-European roots and the English words derived from them is available in our Dictionary of Indo-European Roots.