VOWELS
作者：Ngân Trần Thanh
1. DIPHTHONGS
1.1. CLOSING
1.1.1. Ending in [ ɪ ]
1.1.2. Ending in [ ʊ ]
1.2. CENTRING
1.2.1. Ending in [ ə ]
2. TRIPHTHONGS
2.1. [ aʊə ], [ aɪə ], [ əɪa], [ ɔɪə ], [ əʊə ]
3. CLASSIFICATION
3.1. TONGUE HEIGHT
3.1.1. High vowels
3.1.2. Low vowels
3.1.3. Mid vowels
3.2. PART OF THE TOUNGE
3.2.1. Front vowels
3.2.2. Back vowels
3.2.3. Central vowels
3.3. LIP ROUNDING
3.3.1. Rounded vowels
3.3.2. Unrounded vowels
3.3.3. Neutral vowels