Pinyin Sheets

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

Published 2026-10-06 · Updated 2026-10-06

Mandarin Tone Change Rules: 一, 不 and the Third Tone

Learners usually first meet tones one syllable at a time: mā, má, mǎ, mà. Then they hear real speech and notice that some tones don't behave as the dictionary says. 你好 sounds like ní hǎo, 一个 sounds like yí ge, and 不是 sounds like bú shì.

This is called tone sandhi (连读变调): tones changing when syllables are said together. Mandarin has a small number of regular rules, and once you know them, a lot of confusion disappears. This guide covers the three that matter most for learners, following a standard Putonghua phonetics summary from a Chinese college's language testing station. It also explains how to write the changes, which is where parents and teachers often disagree.

A quick reminder of tone pitch values (5 = high, 1 = low): first tone 55, second tone 35, third tone 214, fourth tone 51.

Rule 1: The third tone

The third tone (上声, pitch 214) is the one that changes most. According to the source above, it generally keeps its full dip-and-rise only when said on its own or at the end of a word or sentence.

Third tone before a non-third tone → low "half-third"

Before a first, second, fourth or neutral tone, the third tone drops its rising tail and is said low (pitch 21):

Combination Examples
3rd + 1st 北方 běifāng, 海关 hǎiguān
3rd + 2nd 祖国 zǔguó, 语言 yǔyán
3rd + 4th 努力 nǔlì, 广大 guǎngdà
3rd + neutral 奶奶 nǎinai, 姐姐 jiějie

The pinyin doesn't change here. You still write běifāng. It's simply how the third tone normally sounds in context. For learners, this means the "low" part is the core of the third tone.

Two third tones together → the first becomes a second tone

When two third tones are next to each other, the first is said like a second tone (pitch 35):

  • 你好 nǐ hǎo → sounds like ní hǎo
  • 旅馆 lǚguǎn → sounds like lúguǎn
  • 粉笔 fěnbǐ → sounds like fénbǐ
  • 保险 bǎoxiǎn → sounds like báoxiǎn

Three third tones

With three third tones in a row, the result depends on how the word is structured (source):

  • Two + one (e.g. 展览馆 = 展览 + 馆, 水彩笔 = 水彩 + 笔): the first two syllables both change to second-tone pitch.
  • One + two (e.g. 纸老虎 = 纸 + 老虎, 党小组 = 党 + 小组): the first syllable is said as a low half-third, and the middle syllable changes to second-tone pitch.

The same source notes that individual speakers vary and that some words aren't worth forcing into a rule. For learners, the two-syllable rule is the one to master. Longer chains sort themselves out with listening.

Does the pinyin change?

Normally, no. Dictionaries, textbooks and our worksheets write the original third tone (nǐ hǎo), and readers apply the change automatically.

Rule 2: 一 (yī)

On its own, 一 is first tone (yī, pitch 55), and it keeps that tone when said alone or at the end of a word or sentence (source). In other positions it changes:

一 before a fourth tone → second tone (yí)

  • 一半 yíbàn
  • 一样 yíyàng
  • 一再 yízài

一 before a first, second or third tone → fourth tone (yì)

  • Before 1st: 一般 yìbān, 一心 yìxīn, 一杯 yì bēi
  • Before 2nd: 一直 yìzhí, 一齐 yìqí, 一同 yìtóng
  • Before 3rd: 一口 yì kǒu, 一早 yìzǎo, 一举 yìjǔ

When 一 doesn't change

  • Counting and numbers: in 十一 and 一百零一, the 一 at the end of the number stays yī.
  • Ordinal meaning ("first"): 一楼 meaning "the first floor / building No. 1" keeps yī. Said with the changed tone, it means "the whole building".

Both points come from the same source. It also notes some disagreement about whether the second 一 in 一百一十一 changes, which is a reminder that not every case is clear-cut.

A practical tip: the measure word 个 is fourth tone in the dictionary, so 一个 becomes yí gè. In everyday speech 个 is often unstressed, but the 一 still sounds like yí.

Rule 3: 不 (bù)

不 is fourth tone (bù, pitch 51). It has only one regular change (source):

不 before a fourth tone → second tone (bú)

  • 不对 búduì
  • 不必 búbì
  • 不但 búdàn
  • 不是 búshì

Before first, second and third tones, 不 stays bù: 不吃 bù chī, 不来 bù lái, 不好 bù hǎo.

A comparison that helps

before 1st/2nd/3rd before 4th
一 yì yí
不 bù (no change) bú

So before a fourth tone, both become second tone. Elsewhere, 一 becomes fourth tone and 不 stays fourth tone.

How should a worksheet write these changes?

This is where people disagree, and both sides have a point.

China's national standard for pinyin orthography, GB/T 16159-2012, says 一 and 不 are generally written with their original tones: yī tiān, bù duì. It also says that in language teaching, they may be written with the changed tones where needed: yì tiān, bú duì (§6.5.2; official record).

So:

  • Writing the original tone (yī, bù) matches dictionaries and most adult materials.
  • Writing the changed tone (yí, yì, bú) matches what a child actually hears and says, and the standard allows it for teaching.

For young children who read pinyin aloud, we suggest changed tones for 一 and 不, and original tones for the third tone (the third-tone change is so automatic that marking it tends to confuse). If your child's school or textbook does something different, follow the school, since consistency matters more than either choice.

In our worksheet generator, you can choose whether 一 and 不 show their spoken tones. Check the highlighted characters before printing either way.

Practice ideas

  • Sort the 一 words. Write ten words containing 一 on cards and have your child sort them into yí and yì piles by looking at the tone of the next syllable.
  • "Not" game. Say a verb; your child says the 不 form with the right tone: 去 → bú qù, 来 → bù lái.
  • Third-tone pairs. Practise 你好, 很好, 水果, 小狗 slowly, then at normal speed.
  • Print and read aloud. Paste a short text with plenty of 一 and 不 into the generator, print it in full mode, and have your child read it aloud before writing.

Sources

Sources