. | 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. | Prosody. the division made in a line or verse by coincidence of the end of a foot and the end of a word. |

di·aer·e·sis (dī-ěr'ĭ-sĭs) n. Variant of dieresis. |
dieresis di·er·e·sis (dī-ěr'ĭ-sĭs)
n.
See solution of continuity.
diaeresis
(from Greek diairein, "to divide"), the resolution of one syllable into two, especially by separating the vowel elements of a diphthong and, by extension, two adjacent vowels, as in the word cooperation; it is also the mark placed over a vowel to indicate that it is pronounced as a separate syllable. In classical prosody, diaeresis refers to the end of a word coinciding with the completion of the metrical foot, in contrast to caesura, which refers to a word ending within a metrical foot
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