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The phonology of Vietnamese features 19 consonant phonemes, with 5 additional consonant phonemes used in Vietnamese's Southern dialect, and 4 exclusive to the Northern dialect. Vietnamese also has 14 vowel nuclei, and 6 tones that are integral to the interpretation of the language. Older interpretations of Vietnamese tones differentiated between "sharp" and "heavy" entering and departing tones. This article is a technical description of the sound system of the Vietnamese language, including phonetics and phonology. Two main varieties of Vietnamese, Hanoi and Saigon, which are slightly different to each other, are described below.

Initial consonants which exist only in the Northern dialect are in red, while those that exist only in the Southern dialect are in blue.

		Labial	Dental/ Alveolar	Retroflex	(Alveolo-) palatal	Velar	Glottal
Nasal		m	n		ɲ	ŋ
Plosive/ Affricate	unaspirated	(p)	t	ʈ	c	k	(ʔ)
	aspirated		tʰ
	implosive	ɓ	ɗ
	affricate				tɕ[a]
Fricative	voiceless	f	s	ʂ		x	h
	voiced	v	z			ɣ
Approximant			l		j	w
Rhotic			r

• /w/ is the only initial consonant permitted to form consonant clusters with other consonants.^[2]
• In many regions of Northern Vietnam, the pair /n/ and /l/ have merged into one, they are no longer two opposing phonemes. Some native Vietnamese speakers who lack linguistic knowledge believe that pronouncing the initial consonant of a word whose orthographic form begins with the letter l as /n/, n as /l/ is nói ngọng.^[3] The phenomenon of no longer distinguishing /n/ from /l/ in words whose orthographic form begins with the letter n or l has three manifestations:^[4]

1. The initial consonant of all words whose orthographic form begins with n or l is /n/.
2. The initial consonant of all words is /l/.
3. In some words, the initial consonant corresponding to the letter n at the beginning of the spelling form of the word is /n/, with l being /l/, in some other words the sound corresponding to n is /l/, with l being /n/.

• In Northern dialects, some words have the initial consonant as the voiced palatal nasal /ɲ/, such as nhuộm, nhức, nhỏ (nhỏ in nhỏ giọt, not nhỏ in nhỏ bé), nhổ, nhốt, have phonetic variants with the initial consonant /z/. This /z/ sound is written with the letter d or gi or r depending on the word (at least one of those three letters, sometimes two, or even all three).^[5]
• Some words with the initial consonant being the voiced velar nasal /ŋ/ also have phonetic variants with the initial consonant being the voiced velar fricative /ɣ/, which are used in some places in the North. For example, the words ngáy (ngáy in ngáy ngủ), ngẫm (ngẫm in suy ngẫm) also have phonetic variants gáy, gẫm.^[6]
• In Northern dialects, the voiceless bilabial plosive /p/ is only the initial consonant in a few loanwords from other languages, mainly from French. In writing, the sound /p/ is written with the letter p, as in sâm panh, derived from French champagne.^[7][1] Not every word in another language that has the initial consonant /p/ have the corresponding Vietnamese loanword with the initial consonant /p/. In some words, the sound /p/ is replaced by the sound /ɓ/. For example, both syllables of the word búp bê (derived from the French word poupée /pu.pe/) have the initial consonant /ɓ/, not /p/.^[8] In Southern dialects, the initial consonant of words whose spelling form begins with the letter p is /ɓ/ in many speakers.^[9]
• The glottalized stops are preglottalized and voiced: [ʔɓ, ʔɗ] (the glottis is always closed before the oral closure). This glottal closure is often not released before the release of the oral closure, resulting in the characteristic implosive pronunciation. However, sometimes the glottal closure is released prior to the oral release in which case the stops are pronounced [ʔb, ʔd]. Therefore, the primary characteristic is preglottalization with implosion being secondary.^[1][10]
• /ɓ, m/ are bilabial, while /f, v/ are labiodental.
• /t, tʰ/ are denti-alveolar ([t̪, t̪ʰ]), while /ɗ, n/ are apico-alveolar.^[1]
• /c, ɲ/ are phonetically lamino-alveolar.^[10]
• /ʈ, c/ are often slightly affricated [ʈ͡ʂ, t͡ɕ], but they are unaspirated.^[10]
• A glottal stop [ʔ] is inserted before words that begin with a vowel or /w/ in Northern dialects:^[2]

ăn	'to eat'	/ăn/	→	[ʔăn]
uỷ	'to delegate'	/wi/	→	[ʔwi˧˩˧]

• /s, z/ are denti-lamino-alveolar: [s̪, z̪].^[11]
• /l/ is apico-alveolar: [l̪].^[1]
• d, gi and r are all pronounced /z/.
• ch and tr are both pronounced /tɕ/,^[a] while x and s are both pronounced /s/.
• The highly salient (and socially stigmatized) merger of /l/ and /n/ as mentioned above, characteristic of the speech of many lower- and working-class Vietnamese in the Red River Delta, is sometimes consciously manipulated to humorous and/or pejorative effect in colloquial Hanoi speech.^[1]
• /p, j, r/ occur in a small number of foreign (mainly French) loans, e.g. [pan˧] < panne 'breakdown', [ɣa˧ ra˧] < garage, [bi˧ ja˧] < billiard. For many speakers, however, /p/ is realized as [b/ɓ] and /r/ as [z].^[1]
• There are no retroflex consonants /ʈʂ/, /ʂ/, /ʐ/, instead there are palato-alveolar consonants: /tʃ/, /ʃ/, /ʒ/ in spelling pronunciations taught in schools.

• /s/ is apico-alveolar [s̺].^[10]
• /l/ is palatalized lamino-alveolar: [lʲ].
• Some people pronounce d as [j], and gi as [z] in situations where the distinction is necessary, most people pronounce both as [j].
• Historically, /v/ is pronounced [j] in common speech, merging with d and gi. However, it is becoming distinct and pronounced as [v], especially in careful speech or when reading a text. In traditional performance including Cải lương, Đờn ca tài tử, Hát bội (Tuồng) and some old speakers of Overseas Vietnamese, it is pronounced as consonant cluster [bj], [βj] or [vj].^[10] In loanwords, it is pronounced [v], [ʋ] or [w], for example, va li is pronounced [vaː˧ lɪi̯˧], [ʋaː˧ lɪi̯˧] or [waː˧ lɪi̯˧].
• Historically, a distinction is made between ch /c/ and tr /ʈ/, as well as between x /s/ and s /ʂ/. However, in many speakers, these two pairs are becoming merged as /c/ and /s/ respectively.^[12]
• In southern speech, the phoneme /r/, generally represented in Vietnamese linguistics by the letter ⟨r⟩, has a number of variant pronunciations depending on the speaker. A person can also have many pronunciations. It may occur as a retroflex fricative [ʐ], an alveolar approximant [ɹ], an alveolar flap [ɾ], a trill [r], or a tapped fricative/fricative trill [ɾ̞, r̝]. In the border area between Ho Chi Minh City and Long An province (Bình Chánh, Cần Giuộc, Cần Đước), the letter ⟨r⟩ is pronounced as a palatal approximant [j]. In many areas in the Mekong Delta, the letter ⟨r⟩ is pronounced as a velar fricative [ɣ].^[13]

As mentioned above, the only cluster in Vietnamese is /Cw/ in which /C/ is a consonant. Southern dialects do not retain this cluster. But this cluster tends to be retained by many young urban people in southern Vietnam, especially in Ho Chi Minh City and surrounding areas. The cluster /Cw/ is reduced to one element. Depending on which consonant forms the cluster /Cw/, there are two patterns in this simplification process. In one pattern the consonant is deleted and /w/ remains. In the other, /w/ is deleted while the consonant remains:^[2]

• In informal speech, /kw/, /hw/, and /ʔw/ are usually pronounced [w]. The cluster go /ɣw/ is very rare, seen only in goá /ɣwa˧˥/ ‘widowed’. ngw /ŋw/ shows greatest loss in rural varieties.

u-/o-	/ʔw/	→	u/o	/w/
hu-/ho-	/hw/	→	u/o	/w/
qu-	/kw/	→	u/o	/w/
go-	/ɣw/	→	o	/w/
ngu-/ngo-	/ŋw/	→	u/o	/w/

However, they are becoming distinct and pronounced as [kw] or [w], [hw], [ʔw], [ɣw], and [ŋw] respectively, especially in formal speech or when reading a text.

• In informal speech, the voiceless velar fricative /x/ (represented by the letter kh) is often transformed into the corresponding voiceless bilabial and labiodental consonants /ɸ/, /f/ and the prevocalic /w/ is deleted, for example: cá khoai is pronounced as cá phai, khóa máy is pronounced as phá máy, khỏe không? is pronounced as phẻ không?. This pronunciation is observed only in rural Southern dialects, and it does not occur in the speech of educated speakers (Nguyễn 2005, Cao and Lê 2005).
• After the bilabial, labiodental consonants /m, ɓ, f, v/ followed by the prevocalic /w/, there are only a few words and most of them are French loanwords, for example: tiền boa (pourboire), đậu pơ-ti-poa (petit pois), xe buýt (bus), vải voan (voile). The initial consonant is kept and the prevocalic /w/ is lost and pronounced as: tiền bo, đậu bo, xe bít, vải von.
• After the consonant clusters of the remaining articulators (alveolar, postalveolar, palatal consonants) followed by the prevocalic /w/, the initial consonant is kept and the prevocalic /w/ is lost as above, for example: vô duyên is pronounced as vô diên, cái loa (hát) is pronounced as cái lo.

The table below summarizes these sound correspondences:

Diaphoneme	Hanoi	Saigon	Example
			word	Hanoi	Saigon
/v/	/v/	/j/ or /v/	vợ   'wife'	[və˨˩ˀ]	[jə˨˧] or [və˨˧]
/z/	/z/	/j/	da   'skin'	[za˧]	[ja˧]
			gia   'to add'
/r/		/r/	ra   'to go out'		[ra˧]
/c/	/c/	/c/	chẻ   'split'	[t͡ɕɛ˧˩]	[cɛ˩˥]
/ʈ/		/ʈ/ or /c/	trẻ   'young'		[ʈɛ˩˥] or [cɛ˩˥]
/s/	/s/	/s/	xinh   'beautiful'	[sɪŋ̟˧]	[sɪ̈n˧]
/ʂ/		/ʂ/ or /s/	sinh   'born'		[ʂɪ̈n˧] or [sɪ̈n˧]

	Front	Central	Back
Centering	/iə̯/ ⟨ia~iê⟩	/ɨə̯/ ⟨ưa~ươ⟩	/uə̯/ ⟨ua~uô⟩
Close	/i/ ⟨i, y⟩	/ɨ/ ⟨ư⟩	/u/ ⟨u⟩
Close-mid/ Mid	/e/ ⟨ê⟩	/ə/ ⟨ơ⟩	/o/ ⟨ô⟩
		/ə̆/ ⟨â⟩
Open-mid/ Open	/ɛ/ ⟨e⟩	/a/ ⟨a⟩	/ɔ/ ⟨o⟩
		/ă/ ⟨ă⟩

The IPA chart of vowel nuclei above is based on the sounds in Hanoi Vietnamese; other regions may have slightly different inventories. Vowel nuclei consist of monophthongs (simple vowels) and three centering diphthongs.

• All vowels are unrounded except for the four back rounded vowels: /u, o, ɔ, uə̯/.
• In the South, the high vowels /i, ɨ, u/ are all diphthongized in open syllables: [ɪi̯, ɯ̽ɯ̯, ʊu̯], Ba Vì [baː˧ vɪi̯˩] (listen^ⓘ).^[14]
• /ə̆/ and /ă/ are pronounced shorter than the other vowels. These short vowels only occur in closed syllables.
• The vowels /ɛː/ and /ɔː/ are marginal. As with the other short/long vowel pairs, short and long /ɛ/ and /ɔ/ are only distinguished in closed syllables. For some speakers the distinction may be one of vowel quality or of the articulation of the syllable coda in addition to or instead of vowel quantity.^[15]
• /ɨ/: Many descriptions, such as Thompson,^[16] Nguyễn (1970), Nguyễn (1997), consider this vowel to be close back unrounded: [ɯ]. However, Han's^[17] instrumental analysis indicates that it is more central than back. Hoang (1965), Brunelle (2003) and Phạm (2006) also transcribe this vowel as central.

In Vietnamese, vowel nuclei are able to combine with offglides /j/ or /w/ to form closing diphthongs and triphthongs. Below is a chart^[18] listing the closing sequences of general northern speech.

	/w/ offglide		/j/ offglide
	Front	Central		Back
Centering	/iə̯w/ ⟨iêu⟩	/ɨə̯w/ ⟨ươu⟩	/ɨə̯j/ ⟨ươi⟩	/uə̯j/ ⟨uôi⟩
Close	/iw/ ⟨iu⟩	/ɨw/ ⟨ưu⟩	/ɨj/ ⟨ưi⟩	/uj/ ⟨ui⟩
Close-mid/ Mid	/ew/ ⟨êu⟩	– /ə̆w/ ⟨âu⟩	/əj/ ⟨ơi⟩ /ə̆j/ ⟨ây⟩	/oj/ ⟨ôi⟩
Open-mid/ Open	/ɛw/ ⟨eo⟩	/aw/ ⟨ao⟩ /ăw/ ⟨au⟩	/aj/ ⟨ai⟩ /ăj/ ⟨ay⟩	/ɔj/ ⟨oi⟩

Thompson (1965) says that in Hanoi, words spelled with ưu and ươu are pronounced /iw, iəw/, respectively, whereas other dialects in the Tonkin delta pronounce them as /ɨw/ and /ɨəw/. This observation is also made by Phạm (2008) and Kirby (2011).

When stops /p, t, k/ occur at the end of words, they have no audible release ([p̚, t̚, k̚]):

đáp	'to reply'	/ɗap/	→	[ɗap̚]
mát	'cool'	/mat/	→	[mat̚]
khác	'different'	/xak/	→	[xak̚]

When the velar consonants /k, ŋ/ are after /u, o, ɔ/, they are articulated with a simultaneous bilabial closure [k͡p̚, ŋ͡m] (i.e. doubly articulated) or are strongly labialized [k̚ʷ, ŋʷ].

đục	'murky'	/ɗuk/	→	[ɗuk͡p̚], [ɗʊk̚ʷ]
độc	'poison'	/ɗok/	→	[ɗə̆wk͡p̚], [ɗə̆wk̚ʷ]
đọc	'to read'	/ɗɔk/	→	[ɗăwk͡p̚], [ɗăwk̚ʷ]
ung	'cancer'	/uŋ/	→	[uŋ͡m], [ʊŋʷ]
ông	'man'/'grandfather'	/oŋ/	→	[ə̆wŋ͡m], [ə̆wŋʷ]
ong	'bee'	/ɔŋ/	→	[ăwŋ͡m], [ăwŋʷ]

The pronunciation of syllable-final ch and nh in Hanoi Vietnamese has had different analyses. One analysis, that of Thompson (1965) has them as being phonemes /c, ɲ/, where /c/ contrasts with both syllable-final t /t/ and c /k/, and /ɲ/ contrasts with syllable-final n /n/ and ng /ŋ/. Final /c, ɲ/ is, then, identified with syllable-initial /c, ɲ/.

Another analysis has final ⟨ch⟩ and ⟨nh⟩ as representing different spellings of the velar phonemes /k/ and /ŋ/ that occur after upper front vowels /i/ (orthographic ⟨i⟩) and /e/ (orthographic ⟨ê⟩). This analysis interprets orthographic ⟨ach⟩ and ⟨anh⟩ as an underlying /ɛ/, which becomes phonetically open and diphthongized: /ɛk/ → [ăjk̟̚], /ɛŋ/ → [ăjŋ̟].^[19] This diphthongization also affects ⟨êch⟩ and ⟨ênh⟩: /ek/ → [ə̆jk̟̚], /eŋ/ → [ə̆jŋ̟].

Arguments for the second analysis include the limited distribution of final [c] and [ɲ], the gap in the distribution of [k] and [ŋ] which do not occur after [i] and [e], the pronunciation of ⟨ach⟩ and ⟨anh⟩ as [ɛc] and [ɛɲ] in certain conservative central dialects,^[20] and the patterning of [k]~[c] and [ŋ]~[ɲ] in certain reduplicated words. Additionally, final [c] is not articulated as far forward as the initial [c]: [c] and [ɲ] are pre-velar [k̟, ŋ̟] with no alveolar contact.^[21]

The first analysis closely follows the surface pronunciation of a slightly different Hanoi dialect than the second. In this dialect, the /a/ in /ac/ and /aɲ/ is not diphthongized but is actually articulated more forward, approaching a front vowel [æ]. This results in a three-way contrast between the rimes ăn [æ̈n] vs. anh [æ̈ɲ] vs. ăng [æ̈ŋ]. For this reason, a separate phonemic /ɲ/ is posited.

The following rimes ending with velar consonants have been diphthongized in the Hanoi dialect, but /i/, /u/ and /ɨ/ are more open:^[20]

ong, oc	/awŋ/, /awk/	→	[ăwŋ͡m], [ăwk͡p̚]
ông, ôc	/əwŋ/, /əwk/	→	[ə̆wŋ͡m], [ə̆wk͡p̚]
ung, uc	/uŋ/, /uk/	→	[ʊŋ͡m], [ʊk͡p̚]
ưng, ưc, ưn, ưt	/ɨŋ/, /ɨk/, /ɨn/, /ɨt/	→	[ɯ̽ŋ], [ɯ̽k̟̚], [ɯ̽n], [ɯ̽t̚]
anh, ach	/ɛŋ/, /ɛk/	→	[ăjŋ̟], [ăjk̟̚]
ênh, êch	/eŋ/, /ek/	→	[ə̆jŋ̟], [ə̆jk̟̚]
inh, ich	/iŋ/, /ik/	→	[ɪŋ̟], [ɪk̟̚]

With the above phonemic analyses, the following is a table of rimes ending in /n, t, ŋ, k/ in the Hanoi dialect:

	/ă/	/a/	/ɛ/	/ɔ/, /aw/	/ə̆/	/ə/	/e/	/o/	/i/	/ɨ/	/u/	/iə̯/	/ɨə̯/	/uə̯/
/n/	ăn	an	en	on	ân	ơn	ên	ôn	in	ưn	un	iên	ươn	uôn
/t/	ăt	at	et	ot	ât	ơt	êt	ôt	it	ưt	ut	iêt	ươt	uôt
/ŋ/	ăng	ang	anh	ong	âng	–	ênh	ông	inh	ưng	ung	iêng	ương	uông
/k/	ăc	ac	ach	oc	âc	–	êch	ôc	ich	ưc	uc	iêc	ươc	uôc

While the variety of Vietnamese spoken in Hanoi has retained finals faithfully from Middle Vietnamese, the variety spoken in Ho Chi Minh City has drastically changed its finals. Rimes ending in /k, ŋ/ merged with those ending in /t, n/, respectively, so they are always pronounced /t, n/, respectively, after the short front vowels /i, e, a/ (only when /a/ is before "nh"). However, they are always pronounced /k, ŋ/ after the other vowels /u, uː, o, ɔ, iː, ɨː, ɨ, aw, a, aː, ɛ, ə, əː/. After rounded vowels /aw, u, o/, many speakers close their lips, i.e. they pronounce /k, ŋ/ as [k͡p, ŋ͡m].^[20] Subsequently, vowels of rimes ending in labiovelars have been diphthongized, while vowels of rimes ending in alveolar have been centralized.^[22] Otherwise, some Southern speakers distinguish /k, ŋ/ and /t, n/ after /u, uː, o, ɔ, iː, ɨː, ɨ, aw, a, aː, ɛ, ə, əː/ in formal speech, but there are no Southern speakers who pronounce "ch" and "nh" at the end of syllables as /k, ŋ/.

The short back vowels in the rimes have been diphthongized and centralized, meanwhile, the consonants have been labialized. Similarly, the short front vowels have been centralized which are realized as central vowels /ă, ə, ɨ/ and the "unspecified" consonants have been affected by coronal spreading from the preceding front vowels which are surfaced as coronals (alveolar) /n, t/.^[20]

ung, uc	/uŋ/, /uk/	→	[ʊwŋ͡m], [ʊwk͡p̚]
ông, ôc	/oŋ/, /ok/	→	[ăwŋ͡m], [ăwk͡p̚]
ong, oc	/ɔŋ/, /ɔk/	→
anh, ach	/an/, /at/	→	[ăn], [ăt̚]
ênh, êch	/en/, /et/	→	[ɤn], [ɤt̚]
in ~ inh, it ~ ich	/in/, /it/	→	[ɪ̈n], [ɪ̈t̚]
um, up	/um/, /up/	→	[ʊm], [ʊp̚]
ưng ~ ưn, ưc ~ ưt	/ɨŋ/, /ɨk/	→	[ɯ̽ŋ], [ɯ̽k̟̚]

The other closed dialects (Huế, Quảng Nam, Bình Định) which have also been merged in codas, but some vowels are pronounced differently in some dialects:

	Huế[23][16]	Quảng Nam[24]	Bình Định[25]	Ho Chi Minh City
ung, uc	[ʊwŋ͡m], [ʊwk͡p̚]	[ʊwŋ͡m], [ʊwk͡p̚]	[ʊwŋ͡m], [ʊwk͡p̚]	[ʊwŋ͡m], [ʊwk͡p̚]
un, ut	[uːŋ͡m], [uːk͡p̚]	[uːŋ͡m], [uːk͡p̚]
ênh, êch	[ən], [ət̚]	[ən], [ət̚]	[ən], [ət̚]	[ɤːn], [ɤːt̚]
ên, êt	[eːn], [eːt̚]	[eːn], [eːt̚]	[eːn], [eːt̚]
inh, ich	[ɪ̈n], [ɪ̈t̚]	[ɪ̈n], [ɪ̈t̚]	[ɪ̈n], [ɪ̈t̚]	[ɪ̈n], [ɪ̈t̚]
in, it	[in], [it̚]	[in], [it̚]	[in], [it̚]

The ông, ôc rimes are merged into ong, oc as [ăwŋ͡m], [ăwk͡p̚] in many Southern speakers, but not with ôn, ôt as pronounced [oːŋ͡m], [oːk͡p̚]. The oong, ooc and eng, ec rimes are few and are mostly loanwords or onomatopoeia. The ôông, ôôc (oong, ooc, eng, ec, êng, êc as well) rimes are the "archaic" form before becoming ông, ôc by diphthongization and still exist in the North Central dialect in many placenames. The articulation of these rimes in the North Central dialect are [oːŋ], [oːk̚] without a simultaneous bilabial closure or labialization.^[26]

on, ot	/ɔn/, /ɔt/	→	[ɔːŋ], [ɔːk]
oong, ooc	/ɔŋ/, /ɔk/	→
ôn, ôt	/on/, /ot/	→	[oːŋ͡m], [oːk͡p̚].
ôông, ôôc	/oŋ/, /ok/	→
ong, oc	/awŋ/, /awk/	→	[ăwŋ͡m], [ăwk͡p̚]
ông, ôc	/əwŋ/, /əwk/	→

With the above phonemic analyses, the following is a table of rimes ending in /n, t, ŋ, k, ŋ͡m, k͡p/ in the Ho Chi Minh City dialect:

	/ɔ/, /aw/	/o/	/u/	/ă/	/a/	/ə̆/	/ə/	/ɨ/	/ɛ/	/e/	/i/	/uː/	/ɨː/	/iː/
/n/				– anh			ên ênh	in inh
/t/				– ach			êt êch	it ich
/ŋ/	on oong			ăn ăng	an ang	ân âng	ơn –	ưn ưng	en eng			uôn uông	ươn ương	iên iêng
/k/	ot ooc			ăt ăc	at ac	ât âc	ơt –	ưt ưc	et ec			uôt uôc	ươt ươc	iêt iêc
/ŋ͡m/	– ong / ông	ôn ôông	un ung
/k͡p/	– oc / ôc	ôt ôôc	ut uc
Combinations that have changed their pronunciation due to merger are bolded.

Vietnamese vowels are all pronounced with an inherent tone. Tones differ in

• pitch
• length
• contour melody
• intensity
• phonation (with or without accompanying constricted vocal cords)

Unlike many Native American, African, and Chinese languages, Vietnamese tones do not rely solely on pitch contour. Vietnamese often uses instead a register complex (which is a combination of phonation type, pitch, length, vowel quality, etc.). Thus, it may be more accurate to categorize Vietnamese as a register language rather than a "pure" tonal language.^[27]

In Vietnamese orthography, tone is indicated by diacritics written above or below the vowel.

There is much variation among speakers concerning how tone is realized phonetically. There are differences between varieties of Vietnamese spoken in the major geographic areas (northern, central, southern) and smaller differences within the major areas (e.g. Hanoi vs. other northern varieties). In addition, there seems to be variation among individuals. More research is needed to determine the remaining details of tone realization and the variation among speakers.

The six tones in the Hanoi and other northern varieties are:

Tone name	Tone ID	Vni/telex/Viqr	Description	Chao Tone Contour	Diacritic	Example
ngang 'flat'	A1	[default]	mid level	˧ (33)	◌	ba ('three')
huyền 'deep'	A2	2 / f / `	low falling (breathy)	˨˩ (21) or (31)	◌̀	bà ('grandmother')
sắc 'sharp'	B1	1 / s / '	mid rising, tense	˧˥ (35)	◌́	bá ('to embrace')
nặng 'heavy'	B2	5 / j / .	mid falling, glottalized, heavy	˧ˀ˨ʔ (3ˀ2ʔ) or ˧ˀ˩ʔ (3ˀ1ʔ)	◌̣	bạ ('to strengthen')
hỏi 'asking'	C1	3 / r / ?	mid falling(-rising), emphasis	˧˩˧ (313) or (323) or (31)	◌̉	bả ('bait')
ngã 'tumbling'	C2	4 / x / ~	mid rising, glottalized	˧ˀ˥ (3ˀ5) or (4ˀ5)	◌̃	bã ('residue')

• The ngang tone is level at around the mid level (33) and is produced with modal voice phonation (i.e. with "normal" phonation). Alexandre de Rhodes (1651) describes this as "level"; Nguyễn (1997) describes it as "high (or mid) level".

• The huyền tone starts low-mid and falls (21). Some Hanoi speakers start at a somewhat higher point (31). It is sometimes accompanied by breathy voice (or lax) phonation in some speakers, but this is lacking in other speakers: bà = [ɓa˨˩].^[28] Alexandre de Rhodes (1651) describes this as "grave-lowering"; Nguyễn (1997) describes it as "low falling".

• The hỏi tone starts a mid level and falls. It starts with modal voice phonation, which moves increasingly toward tense voice with accompanying harsh voice (although the harsh voice seems to vary according to speaker). In Hanoi, the tone is mid falling (31). In other northern speakers, the tone is mid falling and then rises back to the mid level (313 or 323). This characteristic gives this tone its traditional description as "dipping". However, the falling-rising contour is most obvious in citation forms or when syllable-final; in other positions and when in fast speech, the rising contour is negligible. The hỏi also is relatively short compared with the other tones, but not as short as the nặng tone. Alexandre de Rhodes (1651) describes this as "smooth-rising"; Nguyễn (1997) describes it as "dipping-rising".

• The ngã tone is mid rising (35). Many speakers begin the vowel with modal voice, followed by strong creaky voice starting toward the middle of the vowel, which is then lessening as the end of the syllable is approached. Some speakers with more dramatic glottalization have a glottal stop closure in the middle of the vowel (i.e. as [VʔV]). In Hanoi Vietnamese, the tone starts at a higher pitch (45) than other northern speakers. Alexandre de Rhodes (1651) describes this as "chesty-raised"; Nguyễn (1997) describes it as "creaking-rising".

• The sắc tone starts as mid and then rises (35) in much the same way as the ngã tone. It is accompanied by tense voice phonation throughout the duration of the vowel. In some Hanoi speakers, the ngã tone is noticeably higher than the sắc tone, for example: má = ˧˦ (34); mã = ˦ˀ˥ (45). Alexandre de Rhodes (1651) describes this as "acute-angry"; Nguyễn (1997) describes it as "high (or mid) rising".

• The nặng tone starts mid or low-mid and rapidly falls in pitch (32 or 21). It starts with tense voice that becomes increasingly tense until the vowel ends in a glottal stop closure. This tone is noticeably shorter than the other tones. Alexandre de Rhodes (1651) describes this as "chesty-heavy"; Nguyễn (1997) describes it as "constricted".

This section needs expansion. You can help by adding to it. (January 2011)

Tone name	Tone ID	Vni/telex/Viqr	Description	Chao Tone Contour			Diacritic	Example
				Quảng Nam[29]	Bình Định[29]	Ho Chi Minh City[30]
ngang "flat"	A1	[default]	mid flat level	˦˨ (42)	˧ (33)	˦ (44)	◌	ba ('three')
huyền "deep"	A2	2 / f / `	low falling	˧˩ (31)	˧˩ (31)	˧˩ (31)	◌̀	bà ('lady')
hỏi "asking"	C1	3 / r / ?	mid falling-rising	˧˨˦ (324)	˧˨˦ (324)	˨˩˦ (214)	◌̉	bả ('poison')
ngã "tumbling"	C2	4 / x / ~					◌̃	bã ('residue')
sắc "sharp"	B1	1 / s / '	high rising	˦˥ (45)	˦˧˥ (435)	˧˥ (35)	◌́	bá ('governor')
nặng "heavy"	B2	5 / j / .	low falling-rising	˧˨˧ (323)	˦˧˦ (313)	˨˩˨ (212)	◌̣	bạ ('at random')

In Southern varieties, tones ngang, sắc, huyền have similar contours to Northern tones; however, these tones are produced with normal voice instead of breathy voice.

The nặng tone is pronounced as low rising tone (12) [˩˨] in fast speech or low falling-rising tone (212) [˨˩˨] in more careful utterance.

The ngã and hỏi tone are merged into a mid falling-rising (214) [˨˩˦], which is somewhat similar to the hỏi tone of the non-Hanoi Northern accent mentioned above. This merged hỏi–ngã tone is characteristic of Southern Vietnamese accents.^[31][32]

This section needs expansion. You can help by adding to it. (May 2008)

North-central and Central Vietnamese varieties are fairly similar with respect to tone although within the North-central dialect region there is considerable internal variation.

It is sometimes said (by people from other provinces) that people from Nghệ An pronounce every tone as a nặng tone.

An older analysis assumes eight tones rather than six.^[34] This follows the lead of traditional Chinese phonology. In Middle Chinese, syllables ending in a vowel or nasal allowed for three tonal distinctions, but syllables ending with /p/, /t/ or /k/ had no tonal distinctions. Rather, they were consistently pronounced with a short high tone, which was called the entering tone and considered a fourth tone. Similar considerations lead to the identification of two additional tones in Vietnamese for syllables ending in /p/, /t/, /c/ and /k/. These are not phonemically distinct from the sắc and nặng tones, however, and hence not considered as separate tones by modern linguists and are not distinguished in the orthography.

Traditional Tone Category		Register	Tone name	Tone ID	Vni/telex/Viqr	Description	Chao Tone Contour by Location				Diacritic	Example
							Hanoi	Quảng Nam[29]	Bình Định[29]	Ho Chi Minh City[30]
bằng 平 "even"	bình 平 "level"	phù "high"	ngang "flat"	A1	[default]	mid flat level	˧ (33)	˦˨ (42)	˧ (33)	˦ (44)	◌	ba ('three')
		trầm "low"	huyền "deep"	A2	2 / f / `	low falling	˨˩ (21)	˧˩ (31)	˧˩ (31)	˧˩ (31)	◌̀	bà ('lady')
trắc 仄 "oblique"	thượng 上 "rising"	high	hỏi "asking"	C1	3 / r / ?	mid falling-rising	˧˩˧ (313)	˧˨˦ (324)	˧˨˦ (324)	˨˩˦ (214)	◌̉	bả ('poison')
		low	ngã "tumbling"	C2	4 / x / ~	mid rising, glottalized	˧ˀ˥ (3ˀ5~4ˀ5)				◌̃	bã ('residue')
	khứ 去 "departing"	high	sắc "sharp"	B1	1 / s / '	high rising	˧˥ (35)	˦˥ (45)	˦˧˥ (435)	˧˥ (35)	◌́	bá ('governor')
		low	nặng "heavy"	B2	5 / j / .	low falling-rising	˧ˀ˩ʔ (3ˀ1ʔ)	˧˨˧ (323)	˦˧˦ (313)	˨˩˨ (212)	◌̣	bạ ('at random')
	nhập 入 "entering"	high	sắc "sharp"	D1	1 / s / '	high checked rising	˧˥ (35)			˦˥ (45)	◌́	bác ('uncle')
		low	nặng "heavy"	D2	5 / j / .	low checked falling	˧ˀ˩ʔ (3ˀ1ʔ)			˨˩ (21)	◌̣	bạc ('silver')

According to Hannas (1997), there are 4,500 to 4,800 possible spoken syllables (depending on dialect), and the standard national orthography (Quốc Ngữ) can represent 6,200 syllables (Quốc Ngữ orthography represents more phonemic distinctions than are made by any one dialect).^[35] A description of syllable structure and exploration of its patterning according to the Prosodic Analysis approach of J.R. Firth is given in Henderson (1966).^[36]

The Vietnamese syllable structure follows the scheme:

(C₁)(w)V(G|C₂)+T

where

C1 = initial consonant onset w = labiovelar on-glide /w/ V = vowel nucleus

G = off-glide coda (/j/ or /w/) C2 = final consonant coda T = tone.

In other words, a syllable has an obligatory nucleus and tone, and can have an optional consonant onset, an optional on-glide /w/, and an optional coda or off-glide.

More explicitly, the syllable types are as follows:

Syllable	Example	Syllable	Example
V	ê "eh"	wV	uể "sluggish"
VC	ám "possess (by ghosts, in the hands of a person etc.)"	wVC	oán "bear a grudge"
VC	ớt "capsicum"	wVC	oắt "little imp"
CV	nữ "female"	CwV	huỷ "cancel"
CVC	cơm "rice"	CwVC	toán "math"
CVC	tức "angry"	CwVC	hoặc "or"

C₁: Any consonant may occur in as an onset with the following exceptions:

• /p/ does not occur in native Vietnamese words

w: the onglide /w/ (sometimes transcribed instead as labialization [ʷ] on a preceding consonant):

• does not occur after labial consonants /ɓ, f, v, m/
• does not occur after /n/ in native Vietnamese words (it occurs in uncommon Sino-Vietnamese borrowings, such as noãn "ovule")

V: The vowel nucleus V may be any of the following 14 monophthongs or diphthongs: /i, ɨ, u, e, ə, o, ɛ, ə̆, ɔ, ă, a, iə̯, ɨə̯, uə̯/.

G: The offglide may be /j/ or /w/. Together, V and G must form one of the diphthongs or triphthongs listed in the section on Vowels.

• offglide /j/ does not follow the front vowels /i, e, ɛ, iə̯/
• offglide /w/ does not follow the rounded vowels /u, o, ɔ, uə̯/
• with some exceptions (such as khuỷu tay "elbow"), the offglide /w/ cannot occur if the syllable contains a /w/ onglide

C₂: The optional coda C₂ is restricted to labial, coronal, and velar stops and nasals /p, t, k, m, n, ŋ/, which cannot cooccur with the offglides /j, w/.

T: Syllables are spoken with an inherent tone contour:

• Six tone contours are possible for syllables with offglides /j, w/, closed syllables with nasal codas /m, n, ŋ/, and open syllables—i.e., those without consonant codas /p, t, k/.
• If the syllable is closed with one of the oral stops /p, t, k/, only two contours are possible: the sắc and the nặng tones.

Common Vietnamese rimes ^[Notes]

		Zero coda	Off-glide coda		Nasal consonant coda			Stop consonant coda
		∅	/j/	/w/	/m/	/n/	/ŋ/	/p/	/t/	/k/
Vowel nucleus	/ă/		ạy [ăj]	ạu [ăw]	ặm [ăm]	ặn [ăn]	ặng [ăŋ]	ặp [ăp]	ặt [ăt]	ặc [ăk]
	/a/	ạ, (gi)à, (gi)ả, (gi)ã, (gi)á [a]	ại [aj]	ạo [aw]	ạm [am]	ạn [an]	ạng [aŋ]	ạp [ap]	ạt [at]	ạc [ak]
	/ɛ/	ẹ [ɛ]		ẹo [ɛw]	ẹm [ɛm]	ẹn [ɛn]	ạnh [ăjŋ]	ẹp [ɛp]	ẹt [ɛt]	ạch [ăjk]
	/ɔ/	ọ [ɔ]	ọi [ɔj]		ọm [ɔm]	ọn [ɔn]	ọng [ăwŋ]	ọp [ɔp]	ọt [ɔt]	ọc [ăwk]
	/ə̆/		ậy [ə̆j]	ậu [ə̆w]	ậm [ə̆m]	ận [ə̆n]	ậng [ə̆ŋ]	ập [ə̆p]	ật [ə̆t]	ậc [ə̆k]
	/ə/	ợ [ə]	ợi [əj]		ợm [əm]	ợn [ən]		ợp [əp]	ợt [ət]
	/e/	ệ [e]		ệu [ew]	ệm [em]	ện [en]	ệnh [ə̆jŋ]	ệp [ep]	ệt [et]	ệch [ə̆jk]
	/o/	ộ [o]	ội [oj]		ộm [om]	ộn [on]	ộng [ə̆wŋ]	ộp [op]	ột [ot]	ộc [ə̆wk]
	/i/	ị, ỵ [i]		ịu [iw]	ịm, ỵm [im]	ịn [in]	ịnh [iŋ]	ịp, ỵp [ip]	ịt [it]	ịch, ỵch [ik]
	/ɨ/	ự [ɨ]	ựi [ɨj]	ựu [ɨw]			ựng [ɨŋ]		ựt [ɨt]	ực [ɨk]
	/u/	ụ [u]	ụi [uj]		ụm [um]	ụn [un]	ụng [uŋ]	ụp [up]	ụt [ut]	ục [uk]
	/iə/	ịa, (g)ịa, ỵa [iə]		iệu, yệu [iəw]	iệm, yệm [iəm]	iện, yện [iən]	iệng, yệng [iəŋ]	iệp, yệp [iəp]	iệt, yệt [iət]	iệc [iək]
	/ɨə/	ựa [ɨə]	ượi [ɨəj]	ượu [ɨəw]	ượm [ɨəm]	ượn [ɨən]	ượng [ɨəŋ]	ượp [ɨəp]	ượt [ɨət]	ược [ɨək]
	/uə/	ụa [uə]	uội [uəj]		uộm [uəm]	uộn [uən]	uộng [uəŋ]		uột [uət]	uộc [uək]
Labiovelar on-glide followed by vowel nucleus	/ʷă/		oạy, (q)uạy [ʷăj]		oặm, (q)uặm [ʷăm]	oặn, (q)uặn [ʷăn]	oặng, (q)uặng [ʷăŋ]	oặp, (q)uặp [ʷăp]	oặt, (q)uặt [ʷăt]	oặc, (q)uặc [ʷăk]
	/ʷa/	oạ, (q)uạ [ʷa]	oại, (q)uại [ʷaj]	oạo, (q)uạo [ʷaw]	oạm, (q)uạm [ʷam]	oạn, (q)uạn [ʷan]	oạng, (q)uạng [ʷaŋ]	oạp, (q)uạp [ʷap]	oạt, (q)uạt [ʷat]	oạc, (q)uạc [ʷak]
	/ʷɛ/	oẹ, (q)uẹ [ʷɛ]		oẹo, (q)uẹo [ʷɛw]	oẹm, (q)uẹm [ʷɛm]	oẹn, (q)uẹn [ʷɛn]	oạnh, (q)uạnh [ʷăjŋ]		oẹt, (q)uẹt [ʷɛt]	oạch, (q)uạch [ʷăjk]
	/ʷə̆/		uậy [ʷə̆j]			uận [ʷə̆n]	uậng [ʷə̆ŋ]		uật [ʷə̆t]
	/ʷə/	uợ [ʷə]
	/ʷe/	uệ [ʷe]		uệu [ʷew]		uện [ʷen]	uệnh [ʷə̆jŋ]		uệt [ʷet]	uệch [ʷə̆jk]
	/ʷi/	uỵ [ʷi]		uỵu [ʷiw]		uỵn [ʷin]	uỵnh [ʷiŋ]	uỵp [ʷip]	uỵt [ʷit]	uỵch [ʷik]
	/ʷiə/	uỵa [ʷiə]				uyện [ʷiən]			uyệt [ʷiət]
Tone		a /a/, à /â/, á /ǎ/, ả /a᷉/, ã /ǎˀ/, ạ /âˀ/						á /á/, ạ /à/

Below is a table comparing four linguists' different transcriptions of Vietnamese vowels as well as the orthographic representation. Notice that this article mostly follows Han (1966), with the exception of marking short vowels short.

comparison of orthography & vowel descriptions

Orthography	Wikipedia	Thompson[16]	Han[17]	Nguyễn[37]	Đoàn[38]
i/y	i	iː	i	i	i
ê	e	eː	e	e	e
e	ɛ	ɛː	ɛ	a	ɛ
ư	ɨ	ɯː	ɨ	ɯ	ɯ
u	u	uː	u	u	u
ô	o	oː	o	o	o
o	ɔ	ɔː	ɔ	ɔ	ɔ
ơ	ə	ɤː	ɜː	əː	ɤː
â	ə̆	ʌ	ɜ	ə	ɤ
a	a	æː	ɐː	ɐː	aː
ă	ă	ɐ	ɐ	ɐ	a

Thompson (1965) says that the vowels [ʌ] (orthographic â) and [ɐ] (orthographic ă) are shorter than all of the other vowels, which is shown here with the length mark [ː] added to the other vowels. His vowels above are only the basic vowel phonemes. Thompson gives a very detailed description of each vowel's various allophonic realizations.

Han (1966) uses acoustic analysis, including spectrograms and formant measuring and plotting, to describe the vowels. She states that the primary difference between orthographic ơ & â and a & ă is a difference of length (a ratio of 2:1). ơ = /ɜː/, â = /ɜ/; a = /ɐː/, ă = /ɐ/. Her formant plots also seem to show that /ɜː/ may be slightly higher than /ɜ/ in some contexts (but this would be secondary to the main difference of length).

Another thing to mention about Han's studies is that she uses a rather small number of participants and, additionally, although her participants are native speakers of the Hanoi variety, they all have lived outside of Hanoi for a significant period of their lives (e.g. in France or Ho Chi Minh City).

Nguyễn (1997) has a simpler, more symmetrical description. He says that his work is not a "complete grammar" but rather a "descriptive introduction." So, his chart above is more a phonological vowel chart rather than a phonetic one.

• Ngữ âm học