The Vietnamese language has 11 monophthong vowels: i, ê, e, ư, ơ, â, a, ă, u, ô, o. These basic vowels comprise a significant element in Vietnamese pronunciation system.
Therefore, learning how to say these is the VERY FIRST STEP in getting to know the language.
In this video, Mr. Phi compares each vowel with a similar sound in English in the hope that learners can practice it much more easily
Source: Element Vietnamese, p.16-17 , Binh Nhu Ngo,