Not to be confused with the Armenian letter ա
The close back unrounded vowel, or high back unrounded vowel, is a type of vowel sound used in some spoken languages. The symbol in the International Phonetic Alphabet that represents this sound is ⟨ɯ⟩. Typographically a turned letter m, given its relation to the sound represented by the letter u it can be considered a u with an extra "bowl". The sound is sometimes referred to as "unrounded u".
The IPA prefers terms "close" and "open" for vowels, hence the name of this article. However, a large number of linguists, perhaps a majority, prefer the terms "high" and "low", and these are the only terms found in introductory textbooks on phonetics such as those by Peter Ladefoged.
- Its vowel height is close, also known as high, which means the tongue is positioned as close as possible to the roof of the mouth without creating a constriction that would be classified as a consonant.
- Its vowel backness is back, which means the tongue is positioned as far back as possible in the mouth without creating a constriction that would be classified as a consonant.
- It is unrounded, which means that the lips are not rounded.
The symbol ⟨ɯ⟩ is sometimes used for Japanese /u/, but that sound is rounded, albeit with labial compression rather than protrusion. It is more accurately described as an exolabial close back vowel.
See also 
- Lee, Hyun Bok (1999), "Korean", Handbook of the International Phonetic Association:A Guide to the Use of the International Phonetic Alphabet, Cambridge University Press, pp. 120–123, ISBN 0-521-63751-1
- Tingsabadh, M.R. Kalaya; Abramson, Arthur S. (1993), "Thai", Journal of the International Phonetic Association 23 (1): 24–26, doi:10.1017/S0025100300004746