一个语言可能会有和半闭与半开的央元音不同的中央圆唇元音 (a rounded /ə/不过因为没有已知的语言分辨半闭、中与半开的央元音,因此IPA没有这个单独给母音的符号,而代表半闭央圆唇元音的符号/ɵ/经常被用以表示这个元音。如果要表达的更精确,半闭央圆唇元音的符号可能会被与开音符号合用而变成:/ɵ̞/.
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