Recently I started to learn Pinyin. The system is relatively easy to follow but some ambiguity does exist. For example, I found the usage of finals o and uo confusing: why the Pinyin for 波 is bo1, not buo1? and 多 is duo1 instead of do1? Would appreciate if someone could give the reason for such usage.

  • It's a good question. I've been learning Chinese for 3 years and a half and I can't really hear the difference between "mou" and "mo" (both these sounds exist in Chinese). – musialmi Mar 29 at 14:25
  • This point is well explained in episode 14 on labial initials in the (paywalled) Chinesepod series "Say it Right." And I am sure I have seen it explained in other places. But I am not sure enough of the details to explain it, and I cannot find a good explanation free on line now, – Colin McLarty Mar 29 at 16:13
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    Since "buo" and "do" don't exist. I would guess this is just a spelling convention, similar to how you don't write the two dots on the ü when it's after "q", "j", "x", but do write them when it's after "l" or "n". – Sweeper Mar 29 at 16:25
  • @Sweeper Yes that is what I have seen. The best systematic explanation I can find now is at the related question chinese.stackexchange.com/questions/993/… . It is amazing to me how many textbook and other explanations of pinyin feel it important to omit such details. – Colin McLarty Mar 29 at 16:30
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    @musialmi The question is about -uo and -o, not -ou and -o. The latter, which you wrote, are definitely different sounds and there are innumerable minimal pairs you'd confuse if you mix them up. Can you hear the difference between duo and dou, you should be able to hear the difference between mo and mou too. – Olle Linge Mar 30 at 10:41

For all practical purposes, you can think of this as a spelling convention. The finals are pronounced the same, even if all finals are to some extent influenced by the preceding initial.

In Pinyin, there is (almost) no overlap between these two spellings, so any given initial that can be followed by -uo can never be followed by -o and vice versa.

The actual pronunciation is arguably also identical, even though this always sparks emotional arguments when mentioned to native speakers with no training in phonetics (they typically claim that there's an obvious difference). This could be either because they are influenced by orthography (the way the word is spelt influences how they perceive it) or that the coarticulation going on with the preceding syllable in combination with the spelling makes them take note of the difference more than they otherwise would have. The phenomenon that spelling influences how native speakers pronounce words is not uncommon, see for example this list on Wikipedia for examples when this happens in English.

In many narrow transcriptions of Mandarin syllables (such as the one in Duanmu San's The Phonology of Chinese (2007) or Lin Yen-Hwei's The Sounds of Chinese (2007), the -uo and -o finals are transcribed exactly the same way: [ᵂoo], e.g. [pᵂoo] for bo and [tᵂoo] for duo.

This means that the sound is treated as a glide, which in one case gets its own letter in Pinyin, but in the other cases (after b, p, m and f) is merely implied.

I don't know the historical reason for this, though. If you listen to the syllables spelt with only -o, there's a clear glide in there, which is also easy to see if you look at spectrograms in e.g. Praat.

Finally, I said at the beginning that there is almost no overlap between these finals. That's because We do have both wo (which could be thought of as uo) and o, which are clearly different sounds. Since none of these have a normal initial, maybe you could say there's overlap, even though they are spelt differently.

However, while the first is very common (e.g. 我), the second is very rare and could be argued to not be a standard syllable at all. It's normally only used for modal particles like 喔.

I have done several projects that involve recording native speaker audio for all possible syllables, and most recorders (educated native speakers) don't know what to do with o or simply read it as wo, further hinting that this is not normal syllable.

For a clear distinction, check the Pinyin chart over at Chinese Pronunciation Wiki.

Possibly, lo also follows this pattern, which would create an overlap with luo, but then again, lo is used in a similar way to o and not really as a full syllable. It should be abundantly clear that bo, po, mo, fo are not pronounced as lo or o, further indicating that it's mostly about spelling.

I have answered several similar questions here and have collected other potential tricky Pinyin issues here: A guide to Pinyin traps and pitfalls: Learn Mandarin pronunciation.


  • Duanmu, S. (2007). The phonology of standard Chinese. Oxford University Press.
  • Lin, Y. H. (2007). The Sounds of Chinese. Cambridge University Press.
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  • thanks for the elaboration. I believe, even though o is qualified as a final on the Pinyin chart, it's actually not used as a final to be attached to any initials other than bpmfw: it's mainly an element to form other composite finals such as ou, uo, ao, etc. It's easier to just think that b,p,m,f,w all have a diminutive 'u' sound in their pronunciation, hence, uo in this case is "simplified" as o. – techie11 Mar 30 at 14:52
  • This answer is all true, except these are not traps or pitfalls of pinyin. They are rules of pinyin, well known to phonologists. They are traps and pitfalls of deliberately oversimplified textbook descriptions of pinyin. – Colin McLarty Mar 30 at 14:52
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    @ColinMcLarty Well, these are certainly problems for students. Obviously, the article is not aimed at people who have studied Mandarin phonetics and phonology. It's a collection of things that students tend to miss, partly because of lack of proper explanations in textbooks and courses. – Olle Linge Mar 30 at 15:04

I am not a scholar in linguistic, but I am a native speaker. I think I am able to answer this question based on my experience.

All pinyin combinations that include o are listed here

bo po mo fo
duo tuo nuo luo
guo kuo huo

zhuo chuo shuo ruo 
zuo cuo suo

where ShengMu j, q, x, y can not be paired with YunMu o.

It is worth mentioning that ShengMu in PinYin is not the same as a consonant. (YunMu, on the other hand, is exactly the same as a vowel.) The pronunciation of a ShengMu includes the consonant part as well as the vowel part. In other words, when pronouncing a ShengMu alone, each ShengMu has a default YunMu. If I write down the default pronunciation of all ShengMus, they are:

I will use /a/ for pronunciations and a for PinYin writings

/bo/ /po/ /mo/ /fo/
/de/ /te/ /ne/ /le/
/ge/ /ke/ /he/
/ji/ /qi/ /xi/
/zhi/ /chi/ /shi/ /ri/
/zi/ /ci/ /si/
/(y)i/ /(w)u/

Here are my findings:

1, o, when not alone, has the same pronunciation as wo. Because u has the same pronunciation as w, when not used alone, o "should" always be written as uo for consistency.

2, The ShengMu b is pronounced as /buo/. The ShengMu alone is able to represent the pronunciation of 播. But the rule of PinYin is, ShengMu cannot exist without YunMu. So we can use a YunMu that will not affect the pronunciation of the original ShengMu: o. The written PinYin b-o, is pronounced as /buo-o/, which is the same as /buo/, which maintains the pronunciation of b. Same thing for p, m, f.

3, When other ShengMus are combined with uo, the default YunMu /i/ or /e/ are substituted by /uo/ so uo is written in its complete form.

PS: When o is used alone, for example, 哦, it sounds like a short version of ao, similar to the 'o' sound in English word 'or'.

Original answer:



bo po mo fo
duo tuo nuo luo
guo kuo huo
zhuo chuo shuo ruo
zuo cuo suo

其中 jqxy 不可搭配。


bo po mo fo
de te ne le
ge ke he
ji qi xi
zhi chi shi ri
zi ci si
i u

其中带 e 的和带 i 的声母如果搭配 o 都写的是 uo。而本来就带 o 的声母如果搭配 o 写的就是 o。u 与 w 同音,所以 wo 的发音等同于 uo。

其实 o 的发音本身有u的成分,理应全部写为 uo。

带 e 或者 i 的声母加 uo 的韵母时,原本的 e 或者 i 其实是被 uo 取代了。

第一行 bpmf 本身作为声母已经包含了bo po mo fo 所代表的全部发音,理应不再带韵母。但汉语拼音的声母不能单独存在,o的存在可以说是加入了一个不改变声母发音的辅助韵母。换句话说bo真正的读音应该是 buo-o,等同于 buo,写作 bo。

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  • Do you really pronounce bo po mo fo as buo puo muo fuo? That is what your last sentence tells me. – joehua Aug 3 at 22:23
  • @joehua yes that's what I mean. The pronunciation is /buo/ but is written as "bo". – River Aug 3 at 22:34
  • Check out this article blog.udn.com/wangtao/7517887 – joehua Aug 3 at 22:35
  • @joehua That is interesting. It can be a very good example of how 国语 is different from 普通话, and pinyin is different from zhuyin. As I am from North part of PRC, I can tell you we never have any pronunciation like /fuan/. And also /bo/ is also not common: it would be /bao/ if necessary. I guess it is because 国语 is from southern 官话, but 普通话 is form northern 官话. Just my guess. – River Aug 3 at 22:46
  • @joehua It can also be the case that our pronunciation is sime-artificial: the standard of pinyin removed the difference of /bo/ and /buo/ and as a result, 普通话 speaker like me never know there was a difference between /bo/ and /buo/ in some kind of 官话 or dialect in some areas of China. – River Aug 3 at 22:55

Let make the answer simple, for uo and o, you can only choose 1 for a 声母:

  • b, p, f only combine with o, e.g. 波, 博, 婆, 佛,
  • l only combine with `uo', e.g. 罗, 落,

In fact, o sounds like , uo sounds like 乌窝

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