Mandarin has a few tone change (sandhi) rules where a written tone is said differently. The three that matter: (1) two third tones in a row - the first becomes a rising tone, so 你好 nǐ hǎo is said ní hǎo; (2) 不 (bù) becomes bú before another fourth tone (不是 bú shì); (3) 一 (yī) becomes yí before a fourth tone and yì before other tones. Pinyin spelling usually stays the same - only the sound changes.
You learned the four tones, you drilled them one by one - and then a native speaker said 你好 and it didn’t match the tone marks at all. You weren’t mishearing. Chinese has tone sandhi: rules where tones shift when they bump into each other. There are only a handful, they’re completely regular, and once they click your speech stops sounding robotic. Here is every rule that actually matters, with examples you can say out loud.
Rule 1: The third-tone rule (the big one)
This is the rule behind 你好. When two third tones come together, the first one changes to a second (rising) tone. The pinyin is still written with the third-tone mark, but you say it rising.
Notice the rule changes the sound, not the spelling. Dictionaries and textbooks keep the original marks (nǐ hǎo) so you can still see the base tones; your job is to apply the shift automatically when you speak.
Three third tones in a row
When three third tones stack up, group them by meaning and change all but the last to rising. The most common pattern turns the first two into second tones:
| Chinese | Written | Spoken | English |
|---|---|---|---|
| 我很好 | wǒ hěn hǎo | wó hén hǎo | I’m very well |
| 我想买 | wǒ xiǎng mǎi | wó xiáng mǎi | I want to buy |
| 展览馆 | zhǎnlǎnguǎn | zhánlánguǎn | exhibition hall |
Don’t overthink strings of three - in real speech, meaning-groups decide the split, and native speakers vary. Get Rule 1 (two in a row) automatic first; the rest follows.
Rule 2: The half-third tone
A full third tone dips down and then rises back up. But that rise only survives at the end of a phrase or before a pause. When a third tone is followed by a first, second, fourth, or neutral tone, you say only the low, falling part - the “half third.” It stays low and does not rise.
This is the rule that makes a third tone sound “short” and low in fast speech. Trying to force the full dip-and-rise every time is exactly what makes learners sound over-careful and unnatural.
Rule 3: 不 (bù) - the negation that shifts
不 is a fourth tone, bù, by default. But when the next syllable is also a fourth tone, 不 changes to a second tone, bú. Before any other tone it stays bù.
| Chinese | Pinyin | English | Why |
|---|---|---|---|
| 不是 | bú shì | is not | 是 is 4th → bú |
| 不要 | bú yào | don’t want | 要 is 4th → bú |
| 不客气 | bú kèqi | you’re welcome | 客 pulls it... see note |
| 不好 | bù hǎo | not good | 好 is 3rd → stays bù |
| 不来 | bù lái | not coming | 来 is 2nd → stays bù |
Note on 不客气: the trigger is the tone of the very next syllable. 客 (kè) is fourth tone, so 不 becomes bú: bú kèqi. Always look at the syllable immediately after 不.
Rule 4: 一 (yī) - the number that wears three tones
一 is the trickiest, because it takes three different tones depending on what follows. Learn it as a set:
| Context | Tone | Example | English |
|---|---|---|---|
| Alone / counting / ordinal | yī | 一、二、三 · 第一 | one, two, three · first |
| Before a 4th tone | yí | 一个 (yí ge) · 一样 (yíyàng) | one (of) · the same |
| Before 1st tone | yì | 一天 (yìtiān) | one day |
| Before 2nd tone | yì | 一年 (yìnián) | one year |
| Before 3rd tone | yì | 一起 (yìqǐ) | together |
The shortcut: before a fourth tone → yí; before everything else → yì; standing alone → yī. (一个 is yí ge because 个 is underlyingly fourth tone, even though it’s often said neutral.)
The tone-change rules in one glance
- 3rd + 3rd → first becomes rising: 你好 = ní hǎo.
- 3rd before 1/2/4/neutral → half third (low, no rise): 老师 lǎoshī.
- 不 → bú before a 4th tone (不是 bú shì); otherwise bù.
- 一 → yí before 4th, yì before others, yī when counting.
- Pinyin spelling keeps the base tone marks - you apply the shift when speaking.
Hear every tone change, not just read about it
Tone sandhi only sticks when you hear it. Hanzijo gives every word native audio with color-coded tones, so the 你好 shift and the 不/一 changes are baked into how you learn each word. A dedicated tone trainer drills minimal pairs until your ear is sharp, exclusive mnemonics lock the characters in, and one SRS schedule keeps it all in memory. Point the OCR scanner at real signs and menus to practice tones in the wild.
Train Your Tones - FreeFrequently asked questions
Does pinyin spelling change with tone sandhi?
Usually no. For the third-tone rule and the half-third tone, pinyin keeps the original marks (你好 stays nǐ hǎo in writing) and you apply the change when speaking. For 一 and 不, many textbooks do write the shifted tone (yí ge, bú shì) to help learners.
Is the third-tone change compulsory?
Yes - in natural speech it’s automatic and required. Saying two full third tones in a row (nǐ hǎo with both dipping) sounds unnatural and over-pronounced to native ears.
What about the tones of 七 (qī) and 八 (bā)?
Older rules changed 七 and 八 before a fourth tone, but in modern standard Mandarin they simply keep their first tone. Focus your energy on 一 and 不, which really do change.
How do I make tone changes automatic?
Don’t compute them syllable by syllable - learn whole words with their spoken tones from native audio, and review with spaced repetition. After enough reps, ní hǎo and bú shì come out correctly without thinking.
Keep reading
The 4 Chinese Tones: A Complete Guide
What each tone sounds like and how to produce it, from scratch.
Pinyin Pronunciation Guide
Every initial and final, and the sounds English speakers get wrong.
How to Say Hello in Chinese
你好 and 15+ greetings - and the 你好 tone change in action.