In addition to 11 monophthong vowels, the Vietnamese language has 32 diphthongs and 13 triphthongs.
AI, AO, AU, ÂU, AY, ÂY, EO, ÊU, IA, IÊ/YÊ, IU, OA, OĂ, OE, OI, ÔI, ƠI, OO, ÔÔ, UA, UĂ, UÂ, ƯA, UÊ, UI, ƯI,UO, UÔ, UƠ, ƯƠ, ƯU, UY
IÊU/YÊU, OAI, OAO, OAY, OEO, UAO, UÂY, UÔI, ƯƠI, ƯƠU, UYA, UYÊ, UYU
There are 12 vowels which must be followed by:
- a vowel or a final consonant: Â, IÊ, UÂ, UÔ, ƯƠ, YÊ.
- a final consonant: Ă, OĂ, OO, ÔÔ, UĂ, UYÊ.
Also, in Southern dialect, there are some vowels different in the way they are pronounced, compared to Northern one.
Please watch the video below to know more about this.