Diphthong

A diphthong is a vowel whose quality changes significantly in one direction during its pronunciation.


 * "When the medial phase shows an audible change of quality, with the change consistently progressing toward a single target, as it were, then the sound is classified as a diphthong." (Laver 1994:146)

Examples
[ai] in English wine, [au] in English house.

Comments
Often phonologists do not agreee whether a tautosyllabic sequence of two sounds is a diphthong or a sequence of vowel plus glide, or glide plus vowel.

Subtypes

 * falling diphthong
 * rising diphthong
 * light diphthong

Origin
From Greek di-phthongos 'two-sound'. The word is first attested in English in the 15th century.

Related terms

 * monophthong (a vowel whose quality does not change)
 * triphthong (a vowel whose quality changes twice during its pronunciation)
 * diphthongization

Link
Utrecht Lexicon of Linguistics

Other languages
Czech dvouhláska German Diphthong (de)