Synaeresis



In linguistics, synaeresis or syneresis (see American and British spelling differences) is a sound change (metaplasm) by which two vowels are pronounced together rather than separately. The opposite is diaeresis.

Ancient Greek
In Ancient Greek, synaeresis is the pronunciation of two separate vowels as a diphthong (αι ), and diaeresis is the separation of a diphthong into two vowels (αϊ ).

Certain words in Proto-Indo-European had two vowels separated by the consonant s or y (esu "good"). In Greek, this consonant changed to h (ehu), and was lost between vowels (eu). In Homer, the two vowels were sometimes pronounced separately (diaeresis: ) and sometimes together (synaeresis: ). Later in Attic Greek, they were always pronounced together.

Modern Greek
In Modern Greek, where original diphthongs are pronounced as monophthongs, synaeresis is the pronunciation of two vowel sounds as a monophthong (αι, and diaeresis is the pronunciation of the two vowels as a diphthong (αϊ ).

English
Synaeresis often occurs with English reduced vowels, as in Asia ( → ).

Etymology
Synaeresis comes from Greek synaíresis "a taking" or "drawing together", from synairéō — "with" and  "grasp".