Onbin

Onbin is a set of sound changes that occurred in Early Middle Japanese around the end of the eighth century to the beginning of the tenth century, first attested in written texts of the Heian period. Onbin changes affected certain consonant-vowel sequences in non-word-initial position, causing them to become replaced with either a single vowel sound or a single consonant sound. Onbin played a role in diversifying the syllable structure of native Japanese words by creating heavy syllables that ended in two vowels or in a vowel followed by a consonant.

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