It is considered that a consecutive vowel "au" turned into a broad tone, and "ou", "oo" and "eu" turned into compound tones [o?] and [jo?] respectively, but some researchers insist otherwise. |
連続母音「あう(au)」は(開音)に、「おう(ou)」・「おお(oo)」と「えう(eu)」がそれぞれ、(合音)になったと考えられているが、異説もある。 |