information:extraction
Reduced vowels

Some languages, such as English and Russian, have what are called 'reduced', 'weak' or 'obscure' vowels in some unstressed positions. These do not correspond one-to-one with the vowel sounds that occur in stressed position (so-called 'full' vowels), and they tend to be mid-centralized in comparison, as well as having reduced rounding or spreading. The IPA has long provided two letters for obscure vowels, mid ⟨ ə ⟩ and lower ⟨ ɐ ⟩, neither of which are defined for rounding. Dialects of English may have up to four phonemic reduced vowels: /ɐ/, /ə/, and higher unrounded /ᵻ/ and rounded /ᵿ/. (The non-IPA letters ⟨ ᵻ ⟩ and ⟨ ᵿ ⟩ may be used for the latter to avoid confusion with the clearly defined values of IPA letters like ⟨ ɨ ⟩ and ⟨ ɵ ⟩, which are also seen, since the IPA only provides for two reduced vowels.)