The IPA provides two letters forreduced vowels: low/open⟨ɐ⟩ and mid⟨ə⟩. These are not defined for rounding. For languages such as English, French and Russian that have additional or just different reduced vowels, some sources use the non-IPA letters⟨ᵿ⟩ and⟨ᵻ⟩ for high/close rounded and unrounded reduced vowels, or redefine IPA⟨ɵ⟩ as a rounded reduced mid vowel.
