The close back rounded vowel, or high back rounded vowel, is a type of vowel sound used in many spoken languages. The symbol in the International Phonetic Alphabet that represents this sound is , and the equivalent X-SAMPA symbol is u.
In most languages, this rounded vowel is pronounced with protruded lips ('endolabial'). However, in a few cases the lips are compressed ('exolabial').
alternates with labio-velar approximant in certain languages, such as French, and in the diphthongs of some languages, with the non-syllabic diacritic and are used in different transcription systems to represent the same sound.
Close back protruded vowel
The close back protruded vowel is the most common variant of the close back rounded vowel. It is typically transcribed in IPA simply as (the convention used in this article). As there is no dedicated IPA diacritic for protrusion, the symbol for the close back rounded vowel with an old diacritic for labialization, , can be used as an ad hoc symbol . Another possible transcription is or (a close back vowel modified by endolabialization), but that could be misread as a diphthong.