Vietnamese phonology
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 Ho Chi Minh City, which are slightly different to each other, are described below. Initial  consonants. Initial consonants which exist only in the Northern dialect are in red, while those that exist only in the Southern dialect are in blue. Comparison of initials. The table below summarizes these sound correspondences: Vowels. Vowel nuclei. 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. Closing sequences. In Vietnamese, vowel nuclei are able to combine with offglides or to form closing diphthongs and triphthongs. Below is a chart listing the closing sequences of general  northern speech. Finals. When stops occur at the end of words, they have no audible release (): When the velar consonants are after , they are articulated with a simultaneous bilabial closure (i.e. doubly articulated) or are strongly labialized . Hanoi finals. Analysis of final "ch", "nh". The pronunciation of syllable-final "ch" and "nh" in Hanoi Vietnamese has had different analyses. One analysis, that of has them as being phonemes , where contrasts with both syllable-final "t" and "c" and contrasts with syllable-final "n" and "ng" . Final is, then, identified with syllable-initial . Another analysis has final and as representing different  spellings of the velar phonemes and that occur after upper front vowels (orthographic ) and (orthographic ). This analysis interprets orthographic ⟨ach⟩ and ⟨anh⟩ as an underlying , which becomes phonetically open and diphthongized: → , → . This diphthongization also affects ⟨êch⟩ and ⟨ênh⟩: → , → . Arguments for the second analysis include the limited distribution of final and , the gap in the distribution of and which do not occur after and , the pronunciation of ⟨ach⟩ and ⟨anh⟩ as and in certain conservative central dialects, and the patterning of ~ and ~ in certain reduplicated words. Additionally, final is not articulated as far forward as  the initial : and are pre-velar with no alveolar contact. The first analysis closely follows the surface pronunciation of a slightly different Hanoi dialect than the second. In this dialect, the in and is not diphthongized but is actually articulated more forward, approaching a front vowel . This results in a three-way contrast between the rimes "ăn" vs. "anh" vs. "ăng" . For this reason, a separate phonemic is posited. Table of Hanoi finals. The following rimes ending with velar consonants have been diphthongized in the Hanoi dialect, but , and are more open: With the above phonemic analyses, the following is  a table of rimes ending in in the Hanoi dialect: Ho Chi Minh City finals. Merger of finals. 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 merged with those ending in , respectively, so they are always pronounced , respectively, after the short front vowels (only when is before "nh"). However, they are always pronounced after the other vowels . After rounded vowels , many speakers close their lips, i.e. they pronounce as . Subsequently, vowels of rimes ending in labiovelars have  been diphthongized, while vowels of rimes ending in alveolar have been centralized. Otherwise, some Southern speakers distinguish and after in formal speech, but there are no Southern speakers who pronounce "ch" and "nh" at the end of syllables as . Table of Ho Chi Minh City finals. 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 and the "unspecified" consonants have been affected by coronal spreading from the preceding front vowels which are surfaced as coronals (alveolar) . The  other closed dialects (Hue, Quang Nam, Binh Dinh) which have also been merged in codas, but some vowels are pronounced differently in some dialects: The "ông", "ôc" rimes are merged into "ong", "oc" as , in many Southern speakers, but not with "ôn", "ôt" as pronounced , . 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 become "ông", "ôc" by diphthongization and still exist in North Central dialect in many placenames. The articulation of these rimes in North Central  dialect are , without a simultaneous bilabial closure or labialization. With the above phonemic analyses, the following is a table of rimes ending in in the Ho Chi Minh City dialect: Tone. Vietnamese vowels are all pronounced with an inherent tone. Tones differ in 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.). So perhaps a better description would be that Vietnamese is a register language and not a "pure" tonal language. In Vietnamese  orthography, tone is indicated by diacritics written above or below the vowel. Six-tone analysis. 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. Northern varieties. The six tones in the Hanoi and other northern varieties are: Ngang tone: Huyền tone: Hỏi  tone: Ngã tone: Sắc tone: Nặng tone: Southern varieties. 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 "hỏi" tone of non-Hanoi Northern accent mentioned above. North-central and Central varieties. 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. Eight-tone analysis. An older analysis assumes eight tones rather than six. 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 , or 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 , , and . 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. Syllables and phonotactics. According to , 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). 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). The Vietnamese syllable structure follows the scheme: where In other words, a syllable has an obligatory nucleus and tone, and can have an optional consonant onset, an optional on-glide , and an optional coda or off-glide. More explicitly, the syllable types are as follows: C: Any consonant may occur in as an onset with the following exceptions: w: the onglide (sometimes transcribed instead as labialization on a preceding consonant): V: The vowel nucleus V may be any of the following 14 monophthongs or diphthongs: . G: The  offglide may be or . Together, V and G must form one of the diphthongs or triphthongs listed in the section on Vowels. C: The optional coda C is restricted to labial, coronal, and velar stops and nasals , which cannot cooccur with the offglides . T: Syllables are spoken with an inherent tone contour: Notes. Below is a table comparing four linguists' different transcriptions of Vietnamese vowels as well as the orthographic representation. Notice that this article mostly follows , with the exception of marking short vowels short. 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).