Tone Change Rules in Mandarin: Third Tone, 一 (yī) and 不 (bù)

Once you've learned the four tones, you'll notice native speakers don't always use them exactly as written. Certain tones change in predictable ways depending on the tone that follows. These rules are called tone sandhi, and they make you sound much more natural.

Third tone plus third tone

When two third tones come together, the first becomes a second tone. So 你好 (nǐ hǎo, hello) is actually pronounced ní hǎo. Pinyin still writes the original tone marks, so you need to know the rule.

More examples:

• 很好 (hěn hǎo) → hén hǎo
• 老板 (lǎobǎn, boss) → láobǎn
• 手表 (shǒubiǎo, watch) → shóubiǎo

A third tone before other tones

A third tone before a first, second or fourth tone is usually pronounced as a "half third": the tone drops but doesn't rise. Think of wǒ mén (我们) as wǒ with a low, short sound.

不 (bù)

The negation 不 is normally fourth tone: bù. Before another fourth tone, it changes to second tone bú:

• 不是 (bù shì) → bú shì, "is not"
• 不要 (bù yào) → bú yào, "don't want"
• 不对 (bù duì) → bú duì, "not correct"

Before first, second or third tones it stays bù: 不吃 (bù chī), 不来 (bù lái), 不好 (bù hǎo).

一 (yī)

The number one is yī in isolation. In combinations it changes:

• Before a fourth tone, it becomes second tone yí: 一个 (yí gè), 一样 (yí yàng).
• Before first, second or third tones, it becomes fourth tone yì: 一天 (yì tiān), 一年 (yì nián), 一起 (yì qǐ).

In numbers and dates read as digits, it stays yī: 一月 (yī yuè, January), 第一 (dì yī, first).

The neutral tone

Some syllables are unstressed and pronounced short, with no tone: 妈妈 (māma), 谢谢 (xièxie), 的 (de). In dictionaries, these are written without a tone mark or with a dot.

Do I need to write changed tones?

No. Pinyin conventionally writes the base tone, and the changes happen automatically in speech. Textbooks and dictionaries follow the same rule.

Why sandhi matters

Learning words with the changed tones helps you avoid sounding stilted, and improves your listening, since you'll recognise words when they sound different from the written tone.

Practice

1. Say ten third-third combinations aloud, changing the first tone.
2. Practise 不 and 一 with every tone.
3. Listen to native speakers and notice the changes.
4. Check word tones in a dictionary.

Look up word tones with English Chinese Dictionary →