diacritic of 2 dots over a letter, used to mark separately pronounced vowels (ES pingüino, FR maïs, EL πρωτεΐνη), sound change (DE Mütter) or to create new letters (TR büfe, UDM ӝӧк)
It is most often used in this way:
- With a diacritic, one vowel is sounded separately from its neighbour. So, in the word zöology, it is pronounced as a long 'o' followed by a short 'o'. Without the diaeresis, it might be pronounced like the word 'zoo'. It is sometimes described as "two vowel sounds occurring in adjacent syllables". It is often used in names where the last vowel is sounded, as in Chloë or Brontë.
- Umlauts: A diacritic above a vowel can mark a sound shift, forming a new letter (Ä, Ö, Ü).
- Because its origin in Ancient Greek was ζῷον, written with the long 'o' first.