Here's a phonological puzzle for you. Consider the pronunciation of the following words of English:
- wag
- swagger
- wacky
- quack
- swanky
- swan
- wasp
- swamp
- wash
- watch
- wander
- quality
- quantity
- squash
All of them have [w] followed by 'a'; and in the first five, the 'a' is pronounced as [æ], while in the remainder it is pronounced as [ɒ]. Why is this?
There seems to be a historical process that makes the vowel after [w] become a back rounded vowel (in British English at least; in American English, the vowel is [ɑ:], which is back but unrounded). But this process does not occur in some phonological environments. So what is it about the first five words that prevents the 'a' being pronounced as [ɒ]?
The answer is that the consonant following the vowel is velar: [k], [g] or [ŋ]. But what is it about a velar consonant that prevents the preceding vowel becoming a back rounded vowel?
I don't know the answer to this; but it might be that English prefers to have dissimilarity in its syllables, so words with a velar consonant followed by a back vowel followed by another velar consonant, such as kung or gong, are not particularly good words of English. (Of course, gong is a word of English, but then it comes from Malay, so maybe it doesn't count.) There are some exceptions, such as cook and cog; but my impression is that this phonological shape is dispreferred in English.
In contrast, there seems to be no similar restriction in Chinese, where gong is a common syllable shape. Furthermore, the vowel in wang (王, 'king') is more back than the vowel in wan (完, 'late'). So, in Chinese, a vowel between [w] and [ŋ] becomes back, which seems to be the opposite of the process in English.
