The close back unrounded vowel, or high back unrounded vowel,[1] is a type of vowel sound used in some spoken languages. Acoustically it is a close back-central unrounded vowel.[2] 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". It is not to be confused with ⟨uɪ⟩, a sequence of the symbols ⟨u⟩ and ⟨ɪ⟩ (which represent the close back rounded vowel and the near-close front unrounded vowel, respectively), nor with ⟨ω⟩, which is an unofficial symbol for the near-close back unrounded vowel.
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. Unrounded back vowels tend to be centralized, which means that often they are in fact near-back.
It is unrounded, which means that the lips are not rounded.
Possible realization of the unstressed vowel /ɯ/, which is variable in rounding and ranges from central to (more often) back and close to close-mid.[7][8] Corresponds to /əl/ in other accents. Develops from dark L; See New Zealand English phonology
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.
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