As it is extremely hard to find a good online summary of all Pinyin pronunciation rules, I am listening the sounds in a Pinyin chart: https://chinese.yabla.com/chinese-pinyin-chart.php . I have read before that the final -iu is pronounced /iou/, but I can hear the "o" only in tone 3 (eg in Pinyin syllable "liu"). I am unable to hear it in tones 1 (high), 2 (rising) and 4 (falling). Is there vowel reduction in some tones or are those audios in this Pinyin chart bad?

  • I don't think so, because I never feel that way in Mandarin. Wha you said possible exist for third tone because sometimes 3rd tone is much longer than others, making middle part of a diphthong or triphthong much clearer Commented Sep 14, 2019 at 0:17
  • Most native speakers don't have the middle /o/ at all. But for a test, it might become a score point Commented Sep 14, 2019 at 0:19
  • Your first sentence in the first message is somewhat ambiguous and I'm not sure what you meant. You don't think that there is an extra /o/ sound in syllables with the ending -iu OR you do think that the extra sound exists, but that it does not disappears in tones 1, 2 and 4? Commented Sep 14, 2019 at 4:54
  • My Tone never changes my vowel. Commented Sep 14, 2019 at 5:05
  • Understood. And how do you pronounce Pinyin syllable "liu"? [liu] or [liou] ? Commented Sep 14, 2019 at 5:10

3 Answers 3


First, it is important to distinguish between the phonemic pronunciation and the phonetic pronunciation. The first represents how native speakers interpret sounds, the latter interpret how the sounds are effectively performed.

The Pinyin final -iu is phonemically pronounced /jəu/, not /iou/ (reference: https://en.m.wikipedia.org/wiki/Standard_Chinese_phonology#Allophones). When combined with the Pinyin initial l-, that Pinyin final becomes the Pinyin syllable liu, phonemically pronounced /liəu/.

Anyway, much more important to a language learner is the phonetic pronunciation. The phonetic pronunciations of -iu may be [jəu], [jou] or even [jo̝u] (vowel O raises due to assimilation to the adjacent high sounds /j/ and /u/), which sounds similar to /ju/. The latter is the pronunciation in the audio recordings of the Pinyin syllable "liu" in the provided Pinyin table. The same also occurs in the audio recordings of the other Pinyin syllables with the final -iu.

Regarding the 3rd tone pronunciation of a Pinyin syllable with the final "-iu", when pronounced in isolation, it falls ([jo]) and then rises ([u]); in this way, this tone has an effect of separation and therefore tends to block the vowel assimilation that I mentioned before. That's why the [o] sound is heard in this tone and barely heard in the other tones in the audio recordings of the provided Pinyin table.

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    "jou" isn't even an valid syllable in PinYin. What are referring? The 韵母 iou? Commented Sep 18, 2019 at 8:33
  • Also notice in normal continuous speech, 3rd tone is simply low and short as other tones, it doesn't usually have a rising part. So normally, the vowel doesn't change with tones at all. Commented Sep 18, 2019 at 8:42
  • I had meant the Pinyin final "-iu". I have fixed it. Thanks for pointing it out. Commented Sep 18, 2019 at 11:30

I don't think there is a universal rule, but rather you just have to remember it as exceptions. Even for third tone "Liu3", it could be either /liu/ (溜, as in 你中文说得很溜) or /lio/ (六).


in Chinese Pinyin, o is prounounced as wooo,so ou can never occur, because wooou is difficult to prounounce in Chinese Pinyin. Only iu is allowed.

For the case ao, actually is au, but au in handwriting is apt to be confused with an, the latter occurs very frequently in Pinyin. To be distinct to an, the pronounce au is taken over by ao.

  • 1
    "pronounced as wooo" = pronounced as English woo? If that's what you meant, that would sound /wu/ in IPA. Pinyin letter "o" does not have that sound in general; for instance, Pinyin syllables "ao" and "dong" are pronounced /ao/ and /doŋ/ (or /dʊŋ/). Commented Sep 16, 2019 at 3:50
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    Nobody knows what kind of sound you're talking about by just using Latin letters without any symbol system mentioned. And it's Pinyin or PinYin, not Pinying. Commented Sep 17, 2019 at 10:03
  • @AlanEvangelista: I'm guessing that cauckf is talking about the pronunciation of -o by itself as a final in the syllables bo, po, mo, fo.
    – sumelic
    Commented Sep 18, 2019 at 12:53

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