Middle Chinese syllables with the shape CVP where C is a bilabial stop and P is a bilabial underwent dissimilation to CVF, where F = P[-labial]. For instance, Baxter's reconstruction of 法 is *pjop, 品 is *phim, and 凡 is *bjom.

Why did this dissimilation only happen to syllables with bilabial initials and codas, and not syllables with coronal or velar initials and codas?

My pet theory is that they disappeared because they sound inherently funny. (Only kidding.)

  • There is no nasal in 法
    – fefe
    Dec 7, 2012 at 8:21
  • Oops, true. It's just place of articulation then.
    – jogloran
    Dec 7, 2012 at 8:28
  • 1
    That's obvious. We're talking about Middle Chinese here. However, Cantonese has bilabial finals, yet 法 is faat3 because of this dissimilation instead of faap3.
    – jogloran
    Dec 7, 2012 at 8:39
  • 1
    OTOH, Hakka kept some of them as is: 法 fab5 (and other chars with 去).
    – dda
    Dec 7, 2012 at 14:20
  • 1
    And Viêtnamese kept them too: 法 pháp 品 phẩm 凡 phàm.
    – dda
    Dec 7, 2012 at 14:28

1 Answer 1


It's not just Cantonese. In Taiwanese Minnan (which does also preserve the labial final -m, usually), the finals of 法、凡、品 have also become alveolar. Also, most Hakka varieties have made the final of 品 alveolar too.

This phenomenon is examined in p.258 under "Long-distance C..C effects", in the chapter on "Consonant-vowel interaction in Cantonese" by Moira Yip, part of collection of papers published in Studies in Chinese Phonology (1997) ed. Wang Jialing. There, it is argued that it is evidence of consonant-vowel segregation.

Labial dissimilation is among the features of Cantonese investigated in part 6 "Cantonese syllabary" of chapter 3 "Cantonese syllables and words" of Modern Cantonese Phonology (1997) by Bauer & Benedict.

This labial dissimilation in Cantonese affects vowels and labialised velar consonants (e.g. /w/, /kʷ/) too: the front rounded vowels /yː/, /œː/, /ɵy/ are disallowed after labial or labialised consonants as well as before final labial consonants; /ɔː/ and /uː/ also tend to be disallowed before final labial consonants.

Why is it labial dissimilation, and not coronal or dorsal dissimilation? There is acutally some indication that coronal dissimilation is happening between the vowel and final consonant in loanwords into Hong Kong Cantonese, e.g. with /ɔːn/ and /ɔːt/ becoming /ɔːŋ/ and /ɔːk/ respectively. There is already an exclusion of front non-high vowel (/ei/, /ɛː/, /œː/) and of mid /ou/ pairing with a labial or coronal coda consonant; this points to an emerging injunction of mid vowels in general being paired with coronal consonants, i.e. coronal dissimilation. The injunction of high vowels with dorsal consonants isn't quite what one would see as dorsal dissimilation though. See this paper for further details from these English-based loanwords.

Still, labial dissimilation far outweighs coronal and dorsal. This paper argues, based mainly on data from Taiwanese Minnan, that it is not principally markedness that motivates the rime phonotactics, but the phonetics of having unreleased final stops. The difference between vowels in their vowel-consonant transition is the reason why some need not dissimilate; they may diphthongise (adding an excrescent schwa in Taiwanese Minnan), change vowel quality, or even neutralise.

That explanation of course raises the following question: Why in Middle Chinese do all those syllables with labial initials and labial finals also have front vowels or front medials?

  • Thanks for a well-researched answer. I suspected there would be literature about this. Do any of the references suggest when the change took place? As I said above, the fact that Korean borrowings preserve final -m and -p in these cases allows the date of the sound change to be bounded on one side.
    – jogloran
    Dec 9, 2012 at 13:15
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    Sino-Korean vocabulary is generally based on Tang dynasty production (as a rule of thumb anyway). Actually, a later "earlier bound" for dissimilation comes with the production of the Guangyun rime table, which still distinguishes e.g. 法 from 發 in the early Song dynasty, although that source is of course subject to a certain conservatism. Interestingly, with respect to the loss of glides after labial fricatives, Pulleyblank's Middle Chinese: A Study in Historical Phonology, says on p88: "This must have occurred at least by Northern Song and was probably well underway during Tang".
    – Michaelyus
    Dec 18, 2012 at 3:53
  • Wish I could give this another upvote... Apr 10, 2013 at 14:49

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