The Vietic Branch
The Vietic family consists of Vietnamese (the national language of Vietnam), and a number of minority languages found in northern and central Vietnam, and in the Lao border regions.  It is also known, especially in French scholarship, as Viet-Muong, but this more properly designates a sub-group of Vietic. 
    Vietnamese was identified as an MK language more than 150 years ago, and there is now a solid body of work demonstrating its historical affinities.  Nevertheless, many people still resist the notion, believing that its origins lie closer to Thai and/or Chinese. 
    Confusion arose partially because Vietnamese emerged as a national language under foreign domination - in 208 BCE Han China made the small Mon-Khmer kingdom then located in the Red River Delta a tribute state, and later in 111 BCE invaded, creating the province of "Viet Nam" or "Southern Province".  Chinese occupation lasted until 939 CE; and during this thousand-year occupation the Vietnamese culture was thoroughly sinicized. 
    Vietnamese was also influenced by Tai migration from southern China into the Indo-Chinese peninsula; many Tai minorities still live in Northern Vietnam.  As Vietnamese gradually became a monosyllabic tonal language, its superficial resemblance to Chinese and Tai increased.  However, these phonological developments are largely explained as the outcomes of internal changes, and similar developments occurred in closely related Vietic languages that have been affected less by outside forces. 
    From the perspective of comparative reconstruction Vietnamese is problematic, as it is less phonologically and lexically conservative than other Vietic languages.  On the other hand, Vietnamese borrowing can be very important for the reconstruction of Old and Archaic Chinese.  It is also important to clearly separate the linguistic importance of Vietnamese from its political influence.  On balance Vietnamese is simply one member of an internally diverse family, the bulk of which have become marginalised by accident of history. 
    The Vietic grouping can be divided into perhaps 7 coordinate branches, bearing in mind that considerable fieldwork still needs to be done, and new languages may yet be discovered:
  • Viet-Muong, including various dialects of Vietnamese and Mu’o’ng
  • Maleng (~ Malieng, Pakatan, Bo)
  • Arem
  • Ruc, Sach, May, Chu’t
  • Pong, Hung, Tum, Khong-Kheng
  • Cuôi or Thô
  • Ahloa, Ahoa (Thavung)
    Literature discussing the comparative reconstruction of Vietic includes Barker & Barker(1970), Thompson (1976), Sokolovskaya (1978), Ferlus (1974, 1975, 1982, 1991, 1996, 1997, 1998).  This work reveals a variety of phonological features and developments among Vietic languages that correspond to the hypothetical intermediate stages Vietnamese must have gone through on its way to becoming a 6 tone language. 
    Viet-Muong - in addition to about 80 million first and second language speakers of Vietnamese, there about 500,000 mainly hill peoples speaking 30+ dialects of Muong (Mu’o’ng).  Muong is extremely close to Vietnamese: they share about 75% of basic vocabulary, and Muong dialects have 5 and 6 tone systems that parallel Vietnamese.  Muong also has many Tai and Chinese loans, but lacks the more extensive lenitions of initial clusters so emblematic of Vietnamese.  This indicates that Vietnamese and Muong form a sub-group that separated during the first millennium while under Chinese rule.  According to Parkin (1991) Muong is from the Tai word for a territorial division. 
    Thavung is a village name that has become commonly used to refer to the Ahloa and Ahoa dialects (and even some non-Vietic languages) spoken in the Lao-Viet border lands and isolated communities in Laos and even Thailand.  Thavung is a register language, contrasting clear versus breathy phonation.  However, the system is asymmetrical - and has twice as many clear vowels as breathy vowels.  Breathyness developed after voiced initials, although it was blocked by various initial clusters.  Thavung also shows post-glottalised final continuants, e.g. final nasals and resonants can end with or without a glottal restriction.  The combination of register and post-glottalisation produces a 4-way distinction that is conventionally notated like tones. 
   
1 - clear phonation, no final glottal
2 - breathy phonation, no final glottal
3 - clear phonation with final glottal
4 - breathy phonation with final glottal
    Sach, Ruc, May and Chu’t are closely related dilects that straddle the Lao-Viet border.  According to Nguyên Van Lo’i (1993) populations on the Vietnam side are: Scach 615, Ruc 125, May 715 and Chu’t 300+; the Ethnologue lists Sach and Ruc in Laos at 1230 and 500 respectively.  Some good linguistic sources are now available, e.g. Ngyên Van Lo’i (1993), Nguyên Phú-Phong et al (1988).  The languages have phonological systems similar to Thavung, but the registers are associated with pitch differences, so they are further down the path to tonality. 
   
1 - clear phonation, contour 55
2 - breathy phonation, contour 22 and 53
3 - clear phonation, contour 34
4 - clear phonation, glottal restriction, contours 434 and 31
    Maleng dialects are spoken in the same general region as Sach etc.  Nguyên Van Lo’i (1993) gives the population in Vietnam as 320, Parkin (1991) states about 800 in Laos.  The language has the 4 tone system of Sach/Ruc but with some minor pitch differences.  Notably, Maleng preserves the distinction between finals *-l and *-r that has been lost in the rest of the family. 
    Arem appears to be the most conservative Vietic language.  The tiny Arem community living in the Viet-Lao borderlands has 75 members according to Nguyên Van Lo’i (1993), and their language is urgently in need of a full description.  Fortunately we have useful materials from Ferlus' field notes and the joint Vietnamese-Soviet expeditions of the late 1970s (note that the name Arem, is also applied to a Maleng dialect).  Phonetically Arem lacks register, but does have postglottalistion, and preserves the articulation of imploded stops. 
Development of Vietnamese tones from register
The presence of post-glottalistion across Vietic is very significant for the comparative reconstruction, and helps provide one key to the longstanding problem of explaining the development of Vietnamese tones. 
    Vietnamese is normally described as a 6-tone language and on this basis it is often compared typologically to Chinese Min dialects and/or Tai languages.  However, the 6 Vietnamese tones are really 3 tones distributed across 2 registers, the latter being the typical MK registers associated with voiced vs. voiceless initials.  This relation is concealed to some extent in Vietnamese because of the reorganisation of the consonant system, which saw voiceless initials become voiced implosives, and etymological implosives become voiced nasals. 
    The explanation of the origin of Vietnamese tones was famously established by Haudricourt (1952, 1954) on the basis of comparison with Khmu, a northern MK language that preserves final stops and fricatives lost in Vietnamese.  The basic pattern is as follows: firstly a register distinction developed based upon sonority of initials, giving rise to what we now call the 'high' an 'low' series.  The low series have depressed fundamental frequency, giving distinctively lower tone contours.  Additionally those tone contours split under the influence of finals:
  • originally open syllables and those with final *nasals have basically flat pitch contours
  • syllables with final *stops diverged further, with the high series rising in pitch, the low series falling in pitch
  • syllables with final *-h and *-s developed falling-rising contours
    Also, those low series syllables that had a final stop or fricative developed a glottal restriction, realised as a glottal hiatus midway through the phonation of the vowel.  This feature is rather unstable, and has tended to be lost subsequently, or to cause a merger with high-series tones in various dialects.  It is evident that languages such as Thavung and Maleng are intermediate in their development - while they tend to lose final fricatives by merger with -j, -l, -h or -ø, these tend to have the same register/tone outcome as the final stops, so that only a 4-way, rather than 6-way, system has developed. 
    Haudricourt's scheme has taken some criticism, as there remained many apparent exceptions among solid MK etyma.  That his explanation is incomplete is not too surprising, because it was based upon comparison of Vietnamese with Northern Mon-Khmer, rather than internal Vietic comparative reconstruction.  The latter may show MK features that are no longer present (or recognised) in Khmuic.  The Vietic comparative reconstruction indicates that glottalised rimes need to be reconstructed as a feature of the proto-phonology, as etyma with glottalised rimes in Arem and other small Vietic languages with the same tone reflexes are cognate with the otherwise exceptional Vietnamese words. 
    On balance it is clear that Vietic is an important witness of proto Mon-Khmer.  The feature of glottalised rimes is significant, and may or may not be very ancient.  A similar feature is found among some Ta'Oi dialects of Katuic, and Diffloth (1989) suggested that these systems are cognate, and derive from a proto Mon-Khmer creaky voice register.  More recently, in a paper read at SEALS 2001, Ferlus suggested that the glottal feature derives secondarily from initial clusters that condition tense articulation of syllables.  These are important questions that beg for further research. 
References and further reading
  • Barker, M. E. 1968. Vietnamese and Mu’o’ng tone correspondences. Studies in comparative Austroasiatic linguistics, N. Zide (ed.), The Hague, Mouton.
  • Barker, M. E. & M. A. Barker 1970. Proto-Vietnamuong (Annamuong) final consonants and vowels. Lingua 24.3:268-285.
  • Barker, M. E. & M. A. Barker 1976. Muong-Vietnamese-English Dictionary. Summer Institute of Linguistics (microfiche).
  • Diffloth, Gérard. 1989. Proto-Austroasiatic Creaky Voice. Mon-Khmer Studies 15:139-154.
  • Ferlus, Michel. 1979. Lexique thavung-français. Cahiers de Linguistique, Asie Orientale 5:71-94.
  • Ferlus, Michel. 1982. Spirantisation des obstruantes médiales et formation du systèm consonantique du vietnamien. Cahiers de Linguistique, Asie Orientale 11.1:83-106.
  • Ferlus, Michel. 1983. Essai de phonétique historique du môn. Mon-Khmer Studies 12:1-90.
  • Ferlus, Michel. 1991. Vocalisme du Proto-Viet-Muong. Paper circulated at the Twenty-fourth ICS-TL&L. Chiang Mai University, Oct. 10-11, 1991.
  • Ferlus, Michel. 1992a. Essai de phonétique historique du khmer (Du milieu du premier millénaire de notre ère à l'époque actuelle), Mon-Khmer Studies 21:57-89.
  • Ferlus, Michel. 1992b. Histoire abrégée de l'évolution des consonnes initiales du vietnamien et du sino-vietnamien, Mon-Khmer Studies 20:111-125.
  • Ferlus, Michel. 1996. Langues et peuples viet-muong. Mon-Khmer Studies, 26:7-28.
  • Ferlus, Michel. 1997. Problèmes de la formation du systèm vocalique du vietnamien. Cahiers de Linguistique, Asie Orientale, 26.1.
  • Ferlus, Michel. 1998. Les systèmes de tons dans les langues viet-muong. Diachronica 15:1.1-27.
  • Gregerson, Kenneth. 1969. A study of Middle-Vietnamese phonology. Bulletin de la Société des Etudes Indochinoises, 44.2:121-93.
  • Haudricourt, André-Georges. 1952. L'origine môn-khmèr des tons en viêtnamien. Journal Asiatique 240:264-265.
  • Haudricourt, André-Georges. 1953. La place du viêtnamien dans les langues austroasiatiques. Bulletin de la Société de Linguistique de Paris 49.1:122-128.
  • Haudricourt, André-Georges. 1954. De l'origine des tons en viêtnamien. Journal Asiatique 242:69-82.
  • Nguyên Phú Phong, Tràn Trí Doi, Michel Ferlus. 1998. Lexique vietnamien-ruc-français. Paris, Sudestasie.
  • Nguyên Van Lo’i. 1993. Tiêng Ruc. Ha Noi, Nha Xuât Ban Khoa Hoc Xa Hôi.
  • Sokolovskaja, N.K. 1978. Materialy k sravnitel'no-ètimologicheskomu slovar'u v'etmyongskix jazykov. Issledovanija po fonologii i grammatike vostochnyx jazykov, Moskva, Nauka, pp126-80.
  • Sokolovskaja, N.K., and Nguyên Van Tài, 1987. Iazyk Myong: Materialy sovetsko-v'etnamskoi lingvisticheskoi ekspeditsii 1979 goda. Moskva, Nauka.
  • Thompson, Laurence C. 1976. Proto-Viet-Muong Phonology. In Jenner et al. (eds.) Austroasiatic Studies. (1976b), pp 1113-1204.
  • Thompson, Laurence C. 1987. A Vietnamese Reference Grammar. Mon-Khmer Studies 13-14.