English has some words - “diet”, “poem”, “dial”
etc – in which two vowels appearing together are pronounced in
separate syllables. Vietnamese has no equivalent; when two vowels
appear together, the result is a single-syllable
diphthong. This may be an
evenly-stressed diphthong (eg. “nói”
(to speak) is pronounced like the start of English
“noise”), or it may sound almost exactly like one of the vowels
(usually the first) on its own. In the latter case, the diphthong
will generally be pronounced longer than the solitary vowel (eg.
“tiêm” (to inject) is
pronounced like “tim” (heart) except
slower).
Be aware that this is only a guide – these are
pronunciations which are approximately correct and should be
comprehensible to a native speaker of Vietnamese, but native pronunciation will often be far more
complicated (as well as varying wildly depending
on factors such as geographical region). Take these pronunciations as
your starting point, and adapt to however your Vietnamese friends
and/or teachers speak.
a
Varies somewhat depending on
context, between 'a' as in “ban” and
'u' as in 'fun'. Usually 'a' as in "ban".
ai, ay, ăy, ây
'ai' as in “main”.
ao, au, âu
'a' as in “cart” run into 'oo' as in “foot”. The
combination doesn't seem to occur in most English dialects. All
other permutations of 'a', 'ă', 'â' and 'o', 'u' should work the
same if examples exist.
ă
'u' as in “mutt”.
â
'a' as in “far”. This is technically the same shape
as 'ă', but generally longer.
e
'e' as in “men”.
ê
'ai' as in “hair”, 'e' as in 'den' – varies only
in length, except for some diphthongs.
i, y
'i' as in “bin”, usually. Sometimes pronounced like 'u' as in
“fur” (but shorter). Examples include “mình”
(me) and “thích” (to like). When either letter appears alone after a consonant and has
a lengthening tone on it, eg. Mỹ (USA) or
tỉ (billion), the resulting syllable is pronounced as if
there were an 'a' between the consonant and the vowel.
o, ô
'o' as in “fog”.
oi, ôi
'oi' as in “boil”.
ơ
Somewhere between 'a' as in “far” and 'u' as in
“fur”. Varies slightly within that range.
u
'oo' as in “foot”.
ư
'u' as in “fur”, usually.
Note that in some words lengthened by tones, eg. ngư (language),
this letter becomes a diphthong – 'u' as in “fur” merging into
a vowel somewhere between 'oo' as in “foot” and 'o' as in “moss”.
The precise details of the second half aren't important, but it is
important to pronounce a diphthong.
ươ
'u' as in “fur”.