The most striking cases are:

莫 (mo), 我(wo), 坡(po),波(bo),


国(guo), 洛(luo), 错(cuo), etc, with one "u" added, which is unnecessary.

To my ears, they are the same, aren't they?

  • I must say you're right, this is inconsistent. (hence +1). My guess is that if you use (go) for "国", no one will get it right. Same for (lo) and (co).
    – Nobody
    Oct 4, 2023 at 8:37
  • 1
    No, they are not the same. Oct 4, 2023 at 9:27
  • 2
  • @Michaelyus Thanks. But during my preparation of the question, there is no clue or tip or whatever telling me that somebody has asked the same question, that's why I thought I was so smart and creative...LOL. Oct 5, 2023 at 2:26

3 Answers 3


The duplicate question has a correct explanation, but it wasn't explained clear enough.

The final sounds (韵母) of Chinese characters are divided into four types, called 开口呼, 齐齿呼, 合口呼, 撮口呼. The classification is based on the initial shape of your mouth, when you are beginning to pronounce that sound.

The final sounds a, o, e belong to 开口呼, because you simply open your mouth to pronounce these sounds. On the other hand, uo belongs to 合口呼, which means to pronounce this sound you initially close your mouth to pronounce the u sound.

When the initial sound is b, p, m, f and the central vowel is o, theoretically there can be two different sounds:

  1. After closing your mouth to pronounce b, you immediately open your mouth to pronounce o (开口呼);
  2. You keep your mouth closed a little longer, and then open your mouth to pronounce o (合口呼).

If there were a phonemic contrast between the two sounds, the first sound would be considered bo, and the second one would be considered buo. However, this contrast does not exist in the standard variant of Mandarin since 20th century. Therefore, only one of the two transliterations bo and buo can be considered standard.

In 1920 a decision was made to make bo the standard spelling instead of buo. The reason was that "when you pronounce b you already closed your mouth, so there is no need for an extra u marker, even though most people pronounce it in the 合口呼 way. Note that this decision was made in the context of a transliteration system much older than the Pinyin system. When the Pinyin system was designed (in 1958) it inherited many design decisions in older systems, including the decision to drop the u marker when the initial sound is b, p, m, f.


  1. The correct way to pronounce bo, po, mo, fo is buo, puo, muo, fuo;
  2. Because there is no phonemic contrast between bo and buo, it was decided that buo would be simply written as bo, dropping the u marker.
  • 1
    The true phonemic contrast from a historical perspective is between de-duo, te-tuo, se-suo; but there is no *be, *pe, *me, *fe in the standard (although you may hear this accent sometimes). This merged *be-*buo is represented as bo.
    – Michaelyus
    Oct 5, 2023 at 10:04

No error, they are indeed not the same sound. It is possible that you fail to hear the difference from not having quite enough practice yet, or you are listening to an accent/speaker that doesn't differenciate.

The difference is there though. To me the difference is just as clear as hun vs huan or han vs hang :)

  • 3
    it is easy to notice the difference between z and zh, c and ch, s and sh, but the difference you mention is really beyond me and many others, native Mandarin speakers included, to be honest. Oct 5, 2023 at 2:29
  • @NanningYouth its true there are definitely differences even natives don't recognize, all depending on accent. Just like some natives also don't differentiate the three you just mentioned well, or don't differentiate n and l, or don't differentiate whichever other things. Objectively the difference is there in standard mandarin, so thats why its in pinyin :)
    – zagrycha
    Oct 5, 2023 at 22:26
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    They are the same sound in standard mandarin. It's a spelling convention, as there's no need to distinguish bou vs buo (only the latter exists), while there is a need to distinguish gou vs guo (both exist). Oct 11, 2023 at 18:23
  • @StumpyJoePete I still think there is a firm difference in sound, between the "o" in 窩 and the "uo" in 郭 etc. Obviously varies by accent, but in standard mandarin such as newcasters I hear it for sure.
    – zagrycha
    Oct 13, 2023 at 4:01

These sounds are different, "zhùyīn" clearly shows when/why "o" or "uo" is to be used.

莫(mò, ㄇㄛˋ), 我(wǒ, ㄨㄛˇ), 坡(pō, ㄆㄛˉ),波(bō, ㄅ)

国(guó, ㄍㄨㄛˊ), 洛(luò, ㄌㄨㄛˋ), 错(cuò, ㄘㄨㄛˋ)

  • Are you using the Japanese system? Oct 5, 2023 at 2:38
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    @NanningYouth This is not Japanese. See en.wikipedia.org/wiki/Bopomofo The Bopomofo characters were created by Zhang Binglin, taken mainly from "regularized" forms of ancient Chinese characters, the modern readings of which contain the sound that each letter represents. Oct 5, 2023 at 3:09

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