diaeresis
A separation of one syllable (especially a vowel which is a diphthong, that is, beginning with one sound and ending with another) into two distinct syllables; distraction.
countable, uncountable
An occurrence of separate vowel sounds in adjacent syllables without an intervening consonant; a hiatus.
countable, uncountable
The diacritical mark consisting of two dots (¨) placed over a letter (especially the second of two consecutive vowels) to indicate that it is sounded separately, usually as a distinct syllable.
countable, uncountable
Diæreſis is vvhen tvvo points ouer a vovvell diuide it from another vovvel, as bouë, queuë, read bou-e, queu-e, not bo-ue, que-ue.
A division, a separation.
countable, figuratively, rare, uncountable
Where it comes from
Unadapted borrowing from Late Latin diaeresis (“distribution; division of a diphthong into two syllables”), from Ancient Greek δῐαίρεσῐς (dĭaíresĭs, “distribution, division; division of a poetic line when the end of a word and a metrical foot coincide; division of a diphthong into two syllables”), from δῐαιρέω (dĭairéō, “to divide; to distinguish; to resolve a diphthong or contracted form”) + -σῐς (-sĭs, suffix forming abstract nouns or nouns of action, process, or result). Δῐαιρέω (Dĭairéō) is derived from δῐᾰ- (dĭă-, prefix meaning ‘across; through; in different directions’) (ultimately from Proto-Indo-European *dwís (“doubly, twice; in two”)) + αἱρέω (hairéō, “to grasp, seize, take”) (ultimately from Proto-Indo-European *ser- (“to grasp, seize, take”)).
Adapted from the Wiktionary entry diaeresis (CC BY-SA 4.0).