In the middle of the Heian period/h/ became unified with/w/ when not used at the beginning of words, so in the medieval period it was voiced when followed by/a/ and/o/ but not voiced before the other vowels. |
語頭以外の/h/は平安時代中期に/w/と統合したため、中世には/a/・/o/が後に続くときには音になるが、その他の母音の前では発音されない。 |