元音变化尤指因与下一音节的元音或半元音的部分相似而引起的元音变化
半元音是由另一个字母辅助才能够发出声音的字母，比如S或R；
1·A Syllable is a nonsignificant composite sound, made up of a mute and a Letter having a sound (a vowel or semivowel); for GR, without an a, is just as much a Syllable as GRA, with an a.
音节是由一个哑音字母和一个发声字母(元音或者半元音)构成的无意义的复合声音，没有A时GR是一个音节，而有a时gra也是一个音节。
2·Syllable is a nonsignificant composite sound, made up of a mute and a Letter having a sound (a vowel or semivowel); for GR, without an a, is just as much a Syllable as GRA, with an a.
音节是由一个哑音字母和一个发声字母(元音或者半元音)构成的无意义的复合声音，没有A时GR是一个音节，而有a时gra也是一个音节。
3·Syllable is a nonsignificant composite sound, made up of a mute and a Letter having a sound (a vowel or semivowel ); for GR, without an A, is just as much a Syllable as GRA, with an A.
音节是由一个哑音字母和一个发声字母（元音或者半元音）构成的无意义的复合声音，没有A时GR是一个音节，而有A时GRA也是一个音节。