Vietnamese vowels

Vowels

Like other southeast Asian languages, Vietnamese has a comparatively large number of vowels. Below is a vowel diagram of Hanoi Vietnamese.

	Front	Central	Back
High	i [i]	ư [ɨ]	u [u]
Upper Mid	ê [e]	ơ [əː]	ô [o]
Lower Mid	e [ɛ]	â [ə]	o [ɔ]
Low	ă [a] / a [aː]

Front, central, and low vowels (i, ê, e, ư, â, ơ, ă, a) are unrounded, whereas the back vowels (u, ô, o) are rounded. The vowels â [ə] andă [a] are pronounced very short, much shorter than the other vowels. Thus, ơ and â are basically pronounced the same except that ơ[əː] is of normal length while â [ə] is short – the same applies to the vowels long a [aː] and short ă [a].

In addition to single vowels (or monophthongs), Vietnamese has diphthongs and triphthongs. The diphthongs consist of a main vowel component followed by a shorter semivowel offglide to a high front position [ɪ̯], a high back position [ʊ̯], or a central position [ə̯].

Vowel nucleus	Diphthong with front offglide	Diphthong with back offglide	Diphthong with centering offglide	Triphthong with front offglide	Triphthong with back offglide
i	–	iu [iʊ̯]	ia~iê~yê [iə̯]	–	iêu [iə̯ʊ̯]
ê	–	êu [eʊ̯]	–	–	–
e	–	eo [ɛʊ̯]	–	–	–
ư	ưi [ɨɪ̯]	ưu [ɨʊ̯]	ưa~ươ [ɨə̯]	ươi [ɨə̯ɪ̯]	ươu [ɨə̯ʊ̯]
â	ây [əɪ̯]	âu [əʊ̯]	–	–	–
ơ	ơi [əːɪ̯]	–	–	–	–
ă	ay [aɪ̯]	au [aʊ̯]	–	–	–
a	ai [aːɪ̯]	ao [aːʊ̯]	–	–	–
u	ui [uɪ̯]	–	ua~uô [uə̯]	uôi [uə̯ɪ̯]	–
ô	ôi [oɪ̯]	–	–	–	–
o	oi [ɔɪ̯]	–	–	–	–

The centering diphthongs are formed with only the three high vowels (i, ư, u) as the main vowel. They are generally spelled as ia, ưa, uawhen they end a word and are spelled iê, ươ, uô, respectively, when they are followed by a consonant. There are also restrictions on the high offglides: the high front offglide cannot occur after a front vowel (i, ê, e) nucleus and the high back offglide cannot occur after a back vowel (u, ô, o) nucleus.

The correspondence between the orthography and pronunciation is complicated. For example, the offglide [ɪ̯] is usually written as i; however, it may also be represented with y. In addition, in the diphthongs [aɪ̯] and [aːɪ̯] the letters y and i also indicate the pronunciation of the main vowel: ay = ă + [ɪ̯], ai = a + [ɪ̯]. Thus, tay "hand" is [taɪ̯] while tai "ear" is [taːɪ̯]. Similarly, u and o indicate different pronunciations of the main vowel: au = ă + [ʊ̯], ao = a + [ʊ̯]. Thus, thau "brass" is [tʰaʊ̯] while thao "raw silk" is [tʰaːʊ̯].

The four triphthongs are formed by adding front and back offglides to the centering diphthongs. Similarly to the restrictions involving diphthongs, a triphthong with front nucleus cannot have a front offglide (after the centering glide) and a triphthong with a back nucleus cannot have a back offglide.

From the front and back offglides [ɪ̯], [ʊ̯], many phonological descriptions analyze these as consonant glides /j/, /w/. Thus, a word such as đâu "where", phonetically [ɗəʊ̯], would be analyzed phonemically as /ɗəw/.

~Info courtesy of wikipedia~