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Thephonology 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 theVietnamese language, includingphonetics andphonology. Two main varieties of Vietnamese,Hanoi andSaigon, which are slightly different from 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.

• /w/ is the only initial consonant permitted to formconsonant 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 letterl as/n/,n as/l/ isnói ngọng.^[3] The phenomenon of no longer distinguishing/n/ from/l/ in words whose orthographic form begins with the lettern orl has three manifestations:^[4]

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

• In Northern dialects, some words have the initial consonant as thevoiced palatal nasal/ɲ/, such asnhuộm,nhức,nhỏ (nhỏ innhỏ giọt, notnhỏ innhỏ bé),nhổ,nhốt, have phonetic variants with the initial consonant/z/. This/z/ sound is written with the letterd orgi orr 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 thevoiced velar nasal/ŋ/ also have phonetic variants with the initial consonant being thevoiced velar fricative/ɣ/, which are used in some places in the North. For example, the wordsngáy (ngáy inngáy ngủ),ngẫm (ngẫm insuy ngẫm) also have phonetic variantsgáy,gẫm.^[6]
• In Northern dialects, thevoiceless 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 letterp, as insâm panh, derived from Frenchchampagne.^[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 wordbúp bê (derived from the French wordpoupée /pu.pe/) have the initial consonant/ɓ/, not/p/.^[8] In Southern dialects, the initial consonant of words whose spelling form begins with the letterp is/ɓ/ in many speakers.^[9]
• The glottalized stops are preglottalized and voiced:[ʔɓ,ʔɗ] (theglottis is always closed before the oral closure). This glottal closure is often not released before the release of the oral closure, resulting in the characteristicimplosive 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/ arebilabial, while/f,v/ arelabiodental.
• /t,tʰ/ aredenti-alveolar ([t̪,t̪ʰ]), while/ɗ,n/ areapico-alveolar.^[1]
• /c,ɲ/ are phoneticallylamino-alveolar.^[10]
• /ʈ,c/ are often slightlyaffricated[ʈ͡ʂ,t͡ɕ], but they areunaspirated.^[10]
• Aglottal 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/ aredenti-lamino-alveolar:[s̪,z̪].^[11]
• /l/ isapico-alveolar:[l̪].^[1]
• d,gi andr are all pronounced/z/.
• ch andtr are both pronounced/tɕ/,^[a] whilex ands 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 noretroflex consonants/ʈʂ/,/ʂ/,/ʐ/, instead there arepalato-alveolar consonants:/tʃ/,/ʃ/,/ʒ/ in spelling pronunciations taught in schools.

• /s/ isapico-alveolar[s̺].^[10]
• /l/ ispalatalizedlamino-alveolar:[lʲ].
• Some people pronounced as[j], andgi as[z] in situations where the distinction is necessary, most people pronounce both as[j].
• Historically,/v/ is pronounced[j] in common speech, merging withd andgi. However, it is becoming distinct and pronounced as[v], especially in careful speech or when reading a text. In traditional performance includingCải 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 betweench/c/ andtr/ʈ/, as well as betweenx/s/ ands/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 aretroflex fricative[ʐ], analveolar approximant[ɹ], analveolar flap[ɾ], atrill[r], or atapped fricative/fricative trill[ɾ̞,r̝]. In the border area betweenHo Chi Minh City andLong An province (Bình Chánh,Cần Giuộc,Cần Đước), the letter⟨r⟩ is pronounced as apalatal approximant [j]. In many areas in theMekong Delta, the letter⟨r⟩ is pronounced as avelar 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 clustergo/ɣw/ is very rare, seen only ingoá/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, thevoiceless velar fricative/x/ (represented by the letterkh) is often transformed into the correspondingvoiceless bilabial andlabiodental consonants/ɸ/,/f/ and the prevocalic/w/ is deleted, for example:cá khoai is pronounced ascá phai,khóa máy is pronounced asphá máy,khỏe không? is pronounced asphẻ 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 thebilabial,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 asvô diên,cái loa (hát) is pronounced ascái 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˧]

TheIPA chart of vowel nuclei above is based on the sounds in Hanoi Vietnamese; other regions may have slightly different inventories. Vowel nuclei consist ofmonophthongs (simplevowels) and threecentering diphthongs. The Standard Vietnamese vowel inventory comprises 9 monophthong qualities /i e ɛ a ɤ ɯ u o ɔ/ and three falling diphthongs /iə ɯə uə/,^{[16][17][18][19][20]} although other acoustic analysis suggests eleven monophthongs /i e ɛ a ɐ ʌ ɤ ɯ u o ɔ/ and three diphthongs /ie/, /ɯɤ/ and /uo/.^[21]

• All vowels areunrounded 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^ⓘ).^{[22][dead link][better source needed]}
• /ə̆/ and/ă/ arepronounced 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.^[16]
• /ɯ/: Many descriptions, such as Thompson,^[23]Nguyễn (1970),Nguyễn (1997), consider this vowel to beclose back unrounded:[ɯ]. However, Han's^[24] instrumental analysis indicates that it is more central[ɨ] than back.Hoang (1965),Brunelle (2003) andPhạm (2006) also transcribe this vowel as central. But according to Kirby (2011), /ɯ/ is frequently realized as mid centralized [ɯ̌], leading some authors to transcribe it as [ɨ] (Han (1966);Brunelle (2003)).^[16]

In Vietnamese, vowel nuclei are able to combine with offglides/j/ or/w/ to form closingdiphthongs andtriphthongs. Below is a chart^[25] listing the closing sequences of general northern speech.

	/w/ offglide		/j/ offglide
	Front	Central		Back
Centering	/iə̯w/⟨iêu⟩	/ɯə̯w/⟨ươu⟩	/ɯə̯j/⟨ươi⟩	/uə̯j/⟨uôi⟩
Close	/iw/⟨iu⟩	/ɯw/⟨ưu⟩	/ɯj/⟨ưi⟩	/uj/⟨ui⟩
Close-mid/ Mid	/ew/⟨êu⟩	– /ɤ̆w/⟨âu⟩	/ɤj/⟨ơi⟩ /ɤ̆j/⟨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 withưu andươu are pronounced/iw,iəw/, respectively, whereas other dialects in the Tonkin delta pronounce them as/ɯw/ and/ɯəw/. This observation is also made byKirby (2011).

When stops/p,t,k/ occur at the end of words, they haveno 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 stronglylabialized[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-finalch andnh in Hanoi Vietnamese has had different analyses. One analysis, that ofThompson (1965) has them as being phonemes/c,ɲ/, where/c/ contrasts with both syllable-finalt/t/ andc/k/, and/ɲ/ contrasts with syllable-finaln/n/ andng/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 anddiphthongized:/ɛk/ →[ăjk̟̚],/ɛŋ/ →[ăjŋ̟].^[b] 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,^[26] 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.^[27]

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 rimesăn[æ̈n] vs.anh[æ̈ɲ] vs.ăng[æ̈ŋ]. For this reason, a separate phonemic/ɲ/ is posited.^{[citation needed]}

The followingrimes ending withvelar consonants have beendiphthongized in the Hanoi dialect, but/i/,/u/ and/ɯ/ are more open:^[26]

ong,oc	/awŋ/,/awk/	→	[ăwŋ͡m],[ăwk͡p̚]
ông,ôc	/əwŋ/,/əwk/	→	[ə̆wŋ͡m],[ə̆wk͡p̚]
ung,uc	/uŋ/,/uk/	→	[ʊŋ͡m],[ʊk͡p̚]
ưng,ưc,ưn,ưt	/ɯŋ/,/ɯk/,/ɯn/,/ɯt/	→	[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:

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].^[26] Subsequently, vowels of rimes ending in labiovelars have been diphthongized, while vowels of rimes ending in alveolar have been centralized.^[28] 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 beendiphthongized andcentralized, meanwhile, the consonants have been labialized. Similarly, the short front vowels have been centralized which arerealized 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/.^[26]

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:

Theông,ôc rimes are merged intoong,oc as[ăwŋ͡m],[ăwk͡p̚] in many Southern speakers, but not withôn,ôt as pronounced[oːŋ͡m],[oːk͡p̚]. Theoong,ooc andeng,ec rimes are few and are mostly loanwords oronomatopoeia. Theôông,ôôc (oong,ooc, eng,ec, êng, êc as well) rimes are the "archaic" form before becomingông,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 orlabialization.^[32]

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:

Vietnamese vowels are all pronounced with an inherenttone. 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 onpitch contour. Vietnamese often uses instead aregister 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.^[33]

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')

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

• Thehuyền tone starts low-mid and falls (21). Some Hanoi speakers start at a somewhat higher point (31). It is sometimes accompanied bybreathy voice (or lax) phonation in some speakers, but this is lacking in other speakers:bà =[ɓa˨˩].^[34] Alexandre de Rhodes (1651) describes this as "grave-lowering";Nguyễn (1997) describes it as "low falling".

• Thehỏi tone starts a mid level and falls. It starts with modal voice phonation, which moves increasingly towardtense voice with accompanyingharsh 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. Thehỏi also is relatively short compared with the other tones, but not as short as thenặng tone. Alexandre de Rhodes (1651) describes this as "smooth-rising";Nguyễn (1997) describes it as "dipping-rising".

• Thengã tone is mid rising (35). Many speakers begin the vowel with modal voice, followed by strongcreaky 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 aglottal 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".

• Thesắc tone starts as mid and then rises (35) in much the same way as thengã tone. It is accompanied bytense voice phonation throughout the duration of the vowel. In some Hanoi speakers, thengã tone is noticeably higher than thesắc 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".

• Thenặng 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 sectionneeds expansion. You can help byadding to it.(January 2011)

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

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

Thengã andhỏi tone are merged into a mid falling-rising (214) [˨˩˦], which is somewhat similar to thehỏi tone of the non-Hanoi Northern accent mentioned above. This mergedhỏi–ngã tone is characteristic of Southern Vietnamese accents.^[37][38]

This sectionneeds expansion. You can help byadding 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 fromNghệ An pronounce every tone as a nặng tone.

An older analysis assumes eight tones rather than six.^[40] This follows the lead oftraditional Chinese phonology. InMiddle 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 theentering 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 notphonemically distinct from thesắc andnặng tones, however, and hence not considered as separate tones by modern linguists and are not distinguished in the orthography.

According toHannas (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).^[41] 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).^[42]

The Vietnamesesyllable 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 consonantonset, an optional on-glide/w/, and an optionalcoda 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 exception:

• /p/ does not occur in native Vietnamese words

w: the onglide/w/ (sometimes transcribed instead aslabialization[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 uncommonSino-Vietnamese borrowings, such asnoãn "ovule")

V: The vowel nucleus V may be any of the following 14 monophthongs or diphthongs:/i,ɯ,u,e,ɤ,o,ɛ,ʌ,ɔ,ɐ,a,iə̯,ɯə̯,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 askhuỷu 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 inherenttone contour:

• Six tone contours are possible for syllables with offglides/j,w/, closed syllables with nasal codas/m,n,ŋ/, andopen 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: thesắc and thenặng tones.

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

comparison of orthography & vowel descriptions

Orthography	Wikipedia	Thompson[23]	Han[24]	Nguyễn[43]	Đoàn[44]
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] (orthographicâ) and[ɐ] (orthographică) 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, includingspectrograms andformant measuring and plotting, to describe the vowels. She states that the primary difference between orthographicơ &â anda &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. inFrance orHo 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.

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