Close central unrounded vowel
The close central unrounded vowel, or high central unrounded vowel, is a type of vowel sound used in some languages. The symbol in the International Phonetic Alphabet that represents this sound is ⟨ɨ⟩, namely the lower-case letter i with a horizontal bar. Both the symbol and the sound are commonly referred to as barred i.
Some languages feature the near-close central unrounded vowel ( ), which is slightly lower. It is most often transcribed in IPA with ⟨ɨ̞⟩ and ⟨ɪ̈⟩, but other transcriptions such as ⟨ɪ̠⟩ and ⟨ɘ̝⟩ are also possible. In many British dictionaries, this vowel has been transcribed ⟨ɪ⟩, which captures its height; in the American tradition it is more often ⟨ɨ⟩, which captures its centrality, or ⟨ᵻ⟩, which captures both. ⟨ᵻ⟩ is also used in a number of other publications, such as Accents of English by John C. Wells. In the third edition of the Oxford English Dictionary, ⟨ᵻ⟩ represents variation between /ɪ/ and /ə/.
/ɨ/ is uncommon as a phoneme in Indo-European languages, occurring most commonly as an allophone in some Slavic languages, such as Russian. However, it is very common as a separate phoneme in the indigenous languages of the Americas and is often in phonemic contrast with other close vowels such as /i/ and /u/ both in modern living languages as well as reconstructed proto-languages (such as Proto-Uto-Aztecan). Campbell, Kaufman & Smith-Stark (1986) identify the presence of this vowel phoneme as an areal feature of a Mesoamerican Sprachbund (although that is not a defining feature of the entire area).
The sound of Polish ⟨y⟩ is often represented as /ɨ/, but actually it is a close-mid advanced central unrounded vowel, more narrowly transcribed [ɘ̟]. Similarly, European Portuguese unstressed ⟨e⟩, often represented as /ɨ/, is actually a near-close near-back unrounded vowel, more narrowly transcribed using ad hoc symbols such as [ɯ̽] (mid-centralized), [ɯ̟] (fronted) and [ʊ̜] (less rounded i.e. unrounded)