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Legend:unrounded • rounded |
Acentral vowel (also called amixed vowel in some older descriptions) is avowel articulated with the tongue in a position intermediate between that of afront vowel and aback vowel.[1][2]
The termcentral refers to an intermediate value on thebackness dimension and is not synonymous withmid, which refers to an intermediate value on theheight dimension.[1]
In the PHOIBLE 2.0 database (3,020 phoneme inventories), the most frequently reported central-vowel phonemes with dedicated IPA letters are[ə] and[ɨ], occurring in 675 (22%) and 491 (16%) inventories respectively. Other dedicated central-vowel letters such as[ʉ],[ɵ],[ɜ], and[ɞ] are much less common.[3][4][5]
Central vowels are defined primarily by tongue-body position (and often jaw position). Because the vowel space is continuous rather than divided into sharp boundaries, vowels described ascentral may vary in their precise articulation across languages and transcription traditions.[1][6]
The IPA vowel chart (and related "vowel quadrilateral" diagrams) is a conventional schematic representation of vowel qualities. The horizontal axis corresponds to front–central–back tongue position, and the vertical axis corresponds to close–open (high–low) tongue height, with rounding typically represented by paired symbols.[7][8]
In acoustic terms, perceived vowel height and backness correlate (roughly) with the first two vowel formants: higher vowels tend to have lower F1, and more back (and/or more rounded) vowels tend to have lower F2. Central vowels often have intermediate F2 values compared with front and back vowels of similar height.[9][10]
| Central vowel | |
|---|---|
| ◌̈ | |
| IPA number | 415 |
| Encoding | |
| Entity(decimal) | ̈ |
| Unicode(hex) | U+0308 |
On theInternational Phonetic Alphabet vowel chart, central vowels occupy the middle column between front and back vowels.[11]When finer distinctions are needed, central vowel qualities are often transcribed using diacritics such ascentralized (⟨◌̈⟩) andmid-centralized (⟨◌̽⟩), along with diacritics for small height/backness adjustments (e.g.raised ⟨◌̝⟩,lowered ⟨◌̞⟩,advanced ⟨◌̟⟩,retracted ⟨◌̠⟩).[8][11]
The central vowels that have dedicated letters in the IPA include:[11]
In some transcription traditions (for example, in Australian and British phonetics), ⟨ɜ⟩ is often used for a stressed "full" central vowel and ⟨ə⟩ for an unstressed reduced vowel ("schwa"), while other traditions (including many American sources) may use ⟨ə⟩ for a fully realized central vowel as well.[7]
Central vowel qualities that lack dedicated IPA letters are typically written with diacritics indicating centralization or small shifts in vowel height/backness.[8][11]
Common examples include:
