11 single vowels, the 2 short ones, and one sound with two spellings
Vietnamese has 11 single vowel sounds: 9 that can stand alone as open syllables, and 2 short ones (ă, â) that must always be followed by an ending consonant. Master their tongue positions and lengths to hear the difference.
Linguists arrange vowels by where your tongue sits: front of the mouth, central, or back, and how high it rises. Vietnamese fills this map with 11 single vowels.
9 of them can stand alone as a full syllable. Tap each to hear it. The two short vowels, ă and â, sit to the right of their long partners (dashed and silent, because they cannot stand alone). They always need a final consonant, which is the next section.
Dashed gray cells (â, ă) are short vowels that only speak when followed by a final consonant.
2 vowels are the short versions of a and ơ: ă and â. They are shorter, but that is not the whole difference. Your tongue also sits somewhere slightly different, and the vowel clips early.
Length changes meaning in Vietnamese. căm and cam are different words, and so are câm and cơm. Listen for how ă and â cut off early, always rushing into the consonant that follows.
Each pair differs only in the vowel: short ă/â against long a/ơ.
That short length is also why they cannot end a syllable. A bare ă or â never appears. They always lean on a closing consonant: ăm, ăn, ăp, âm, ân, ât, and so on.
Both vowels are short. The final consonant is what lets them be spoken: ă vs â.
e vs ê: e is the open "eh" of "bed". ê is tighter, close to the "ay" of "bay" without the glide English adds. Compare xe vs xê, me vs mê, đe vs đê.
o vs ô: o is the open "aw" of "law". ô is rounder, a pure "oh" with the lips pursed. Compare co vs cô, lo vs lô, to vs tô.
u vs ư: say "oo" as in "food", then unround your lips into a smile and keep your tongue high and back. That is ư. Compare thu vs thư, su vs sư, tu vs tư.
As the main vowel of a syllable, i and y both say /i/. The choice is spelling convention, not pronunciation. bánh mì and bánh mỳ are the same word.
Two spellings, one pronunciation.
One spot is fixed. After qu, the vowel is always written y (quý, quy). In qu, the u is not a vowel. It is part of the /kʷ/ sound, so y carries the vowel.
Outside those spots, the spelling leans on a word's origin. y is common in Sino-Vietnamese words, the vocabulary borrowed from Chinese (y as in y học, mỹ, kỳ). Native Vietnamese words usually take i, even when a syllable starts on the vowel (ỉ as in lợn ỉ, dì, đi).
One caution: this only holds when i or y is the main vowel. When it joins another vowel letter, it takes on a different sound. That is covered in a later post.
Spelling stays the same across Vietnam, but a vowel's actual sound can shift depending on what comes after it, and where you are.
Vowel drift in the South: Southern speakers let high vowels shift as they speak. mi, tu, and tư start relaxed and tighten at the end, while Hà Nội holds one steady note.
Open i, u, ư drift in Sài Gòn: subtle to hear, but real.
Endings change the vowel: More noticeably, certain closing consonants pull the vowel away from its standard sound: