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In page Fricative:

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Phonemically nasalized fricatives are rare. Umbundu has /ṽ/[citation needed] and Kwangali and Souletin Basque have /h̃/. In Coatzospan Mixtec, [β̃, ð̃, s̃, ʃ̃] appear allophonically before a nasal vowel, and in Igbo nasality is a feature of the syllable; when /f v s z ʃ ʒ/ occur in nasal syllables they are themselves nasalized.[1]