Mandarin Tone Sandhi: The Third Tone, 一 (yī) and 不 (bù)

Tone sandhi means that some tones change depending on the tone that follows. Three rules cover nearly everything a learner needs: two third tones in a row, the word 一 "one", and the word 不 "not". All three affect some of the most common expressions in the language, starting with nǐ hǎo.

Rule 1: third tone + third tone

When a third tone is followed by another third tone, the first one changes to a second tone:

The reason is physical: a full third tone dips low and then rises, and saying two in a row is awkward. In practice, the changed tone sounds identical to a real second tone, so 买马 mǎi mǎ "buy a horse" sounds like mái mǎ, and 起码 qǐmǎ sounds like 骑马 qímǎ.

Half third tone

A related rule: a third tone before a first, second, fourth or neutral tone is pronounced as a "half third tone", low and without the final rise: 老师 lǎoshī [21 55], 我们 wǒmen. This is not usually called sandhi, but it is the normal pronunciation, and it is why the third tone is best thought of as a low tone.

Three or more third tones

With longer chains, the result depends on how the words group together. The last syllable keeps its third tone, and the others generally become second tones, working within each word or phrase:

• 我很好 wǒ hěn hǎo → usually wó hén hǎo
• 展览馆 zhǎnlǎnguǎn (exhibition hall) → zhánlánguǎn
• 我想买 wǒ xiǎng mǎi → in fast speech, wó xiáng mǎi

Rule 2: 一 yī "one"

一 has its original first tone when it stands alone, at the end of a word, when counting, and in ordinal numbers. Otherwise it changes:

Rule 3: 不 bù "not"

不 is fourth tone, except before another fourth tone, where it becomes second tone:

The logic is the same as for third tones: two sharp falls in a row are awkward, so the first becomes a rise.

The glosses above show the pronounced tones, not the dictionary tones, so you can see where the rules apply.

Frequently asked questions

Is third-tone sandhi written in pinyin?

No. Pinyin always shows the original tone: 你好 is written nǐ hǎo, even though it is pronounced ní hǎo. The change is automatic, so you apply it when speaking.

Is the tone change of 一 and 不 written in pinyin?

Dictionaries write the original tones (yī, bù), but many textbooks mark the changed tone to help learners: yí gè, bú shì. Both conventions are common, so check which one your textbook uses.

What happens with three third tones in a row?

It depends on how the words group. In 我很好 (wǒ hěn hǎo), 很好 forms a unit, and the usual pronunciation is wó hén hǎo. Groupings that split differently can give different results, but in fast speech the first two often both become second tones.

Sources and further reading

• Chen, M. Y. (2000). Tone Sandhi: Patterns across Chinese Dialects. Cambridge University Press.
• Duanmu, S. (2007). The Phonology of Standard Chinese (2nd ed.), chapter 11 on tone sandhi. Oxford University Press.
• Shih, C. (1986). The Prosodic Domain of Tone Sandhi in Chinese. Doctoral dissertation, University of California, San Diego.

Read More in This Topic

• The Four Tones of Mandarin Chinese: How to Hear and Say Them
• Mandarin Tone Pairs: Practising Tones in Two-Syllable Words
• Pinyin Spelling Rules: Y, W, Apostrophes and Where the Tone Mark Goes

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