Near-close near-back rounded vowel
The near-close back rounded vowel, or near-high back rounded vowel, is a type of vowel sound, used in some vocal languages. The IPA symbol that represents this sound is ⟨ʊ⟩. It is informally called "horseshoe u". Prior to 1989, there was an alternative IPA symbol for this sound, ⟨ɷ⟩, called "closed omega"; use of this symbol is no longer sanctioned by the IPA. In Americanist phonetic notation, the symbol ⟨ᴜ⟩ (a small capital U) is used. Sometimes, especially in broad transcription, this vowel is transcribed with a simpler symbol ⟨u⟩, which technically represents the close back rounded vowel.
|Near-close back rounded vowel|
Vowels beside dots are: unrounded • rounded
Handbook of the International Phonetic Association defines [ʊ] as a mid-centralized (lowered and centralized) close back rounded vowel (transcribed [u̽] or [ü̞]), and the current official IPA name of the vowel transcribed with the symbol ⟨ʊ⟩ is near-close near-back rounded vowel. However, some languages have the close-mid near-back rounded vowel, a vowel that is somewhat lower than the canonical value of [ʊ], though it still fits the definition of a mid-centralized [u]. It occurs in some dialects of English (such as General American and Geordie) as well as some other languages (such as Maastrichtian Limburgish). It can be transcribed with the symbol ⟨ʊ̞⟩ (a lowered ⟨ʊ⟩) in narrow transcription. For the close-mid (near-)back rounded vowel that is not usually transcribed with the symbol ⟨ʊ⟩ (or ⟨u⟩), see close-mid back rounded vowel.
In some other languages (such as Bengali and Luxembourgish) as well as some dialects of English (such as Scottish) there is a fully back near-close rounded vowel (a sound between cardinal [u] and [o]), which can be transcribed in IPA with ⟨ʊ̠⟩, ⟨u̞⟩ or ⟨o̝⟩. There may be phonological reasons not to use the first symbol, as it may incorrectly imply a relation to the fully close [u]. It also implies too weak a rounding in some cases (specifically in the case of the vowels that are described as tense in Germanic languages), which would have to be specified as ⟨ʊ̹˗⟩ anyway.
A few languages also have the near-close back unrounded vowel in their inventory. This does not have a separate IPA letter, but may be specified as ⟨ɯ̽⟩. In Russian use of the IPA, the letter ⟨ъ⟩ may fill in this spot.