Tones of 一 yī and 不 bù

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Grammar · HSK 1
Grammar Point · HSK 1

一 yī & 不 bù — tone changes

The tones of 一 yī and 不 bù change depending on the syllable that comes after them. It’s confusing at first, but the rules are simple, so let’s go through them together!

Tones of 一 yī and 不 bù

The key is always the next syllable. Before a 4th tone, both 一 yī and 不 bù rise to the 2nd tone (yí, bú). In the tone marks below, the changing 一 yī and 不 bù are highlighted in red.

1Quick Overview

When一不
On its own, counting, ordinal numbers, or at the end of a wordyībù
Before a 1st, 2nd, or 3rd toneyìbù
Before a 4th tone (or a light syllable that was originally 4th tone, like 个 ge)yíbú

2一 yī

Stays yī: counting, ordinals, and at the end of a word

When you count numbers, read out digits, use 一 yī as an ordinal (“first”), or when 一 yī is the last character of a word, it keeps its original 1st tone.

一yī、二èr、三sān、四sì
one, two, three, four
十shí一yī点diǎn
11 o’clock
第dì一yī
first
周zhōu一yī
Monday
唯wéi一yī
only
2èr0líng1yī1yī年nián
the year 2011
一yī月yuè
January (exception)
📌 Exception: months

Even though 月 yuè is a 4th tone, 一月 yīyuè (“January”) keeps yī, because here 一 yī works like an ordinal number (“month one”), not a quantity.

Becomes yì: before a 1st, 2nd, or 3rd tone

When 一 yī comes before a measure word or another syllable in the 1st, 2nd, or 3rd tone, it changes to the 4th tone.

一yì本běn书shū
a book
一yì百bǎi
100
一yì千qiān
1,000
一yì起qǐ
together
一yì些xiē
some

Becomes yí: before a 4th tone

When the next syllable is a 4th tone (or a light syllable that was originally 4th tone), 一 yī changes to the 2nd tone.

一yí件jiàn衣服yīfu
one piece of clothing
一yí样yàng
the same
一yí半bàn
half
一yí万wàn
10,000

Special case in China: yāo

一 yī and 七 qī can sound alike, so in mainland China 一 yī is often read as yāo when giving phone numbers, hotel room numbers, and 3-digit bus numbers.

我wǒ的de房fáng号hào是shì123yāo·èr·sān
My room number is 123.

3不 bù

不 bù follows the same idea as 一 yī, but it only has two forms.

Stays bù: before a 1st, 2nd, or 3rd tone

不bù好hǎo
not good
不bù知道zhīdào
don’t know
不bù能néng
can’t

Becomes bú: before a 4th tone

不bú要yào
don’t want
不bú会huì
won’t / can’t
不bú是shì
is not
💡 FYI

Many dictionaries and textbooks always write the original tones, yī and bù, and leave the change to you. On this site we mark the tone you actually say, so you’ll see yì, yí, and bú in our examples.

4Common Mistakes

❌一yí月yuè
✅一yī月yuè
In months, 一 yī is an ordinal (“month one”), so it stays yī even before the 4th tone.
❌第dì一yí次cì
✅第dì一yī次cì
After 第 dì, 一 yī means “first” and stays yī.
❌不bù是shì
✅不bú是shì
是 shì is a 4th tone, so 不 bù must change to bú.

5Practice

Try to read the following words:

Listen: 一 yī words

一 tiān　一 wèi　一 zhī　一 tiáo　一 wàn　一 diǎn　一 tái　一 fēn　一 běn　一 ge　一 bēi　一 dài　一 zhí　一 zhǒng　一 fèn　一 yàng

Listen: 不 bù words

不 yào　不 xiǎng　不 kěyǐ　不 zhīdào　不 dǒng　不 qù　不 lái　不 shuìjiào　不 xǐhuan　不 fāngbiàn　不 dà　不 xiǎo　不 cháng　不 duǎn　不 pàng　不 shòu　不 néng　不 huì

Now pick the correct tone for 一 yī or 不 bù in each word.

Question 1 of 34

一天tiān (day)

天 tiān is 1st tone, so 一 yī becomes yì.

一位wèi (person (polite))

位 wèi is 4th tone, so 一 yī becomes yí.

一只zhī ((animals))

只 zhī is 1st tone, so 一 yī becomes yì.

一条tiáo ((long things))

条 tiáo is 2nd tone, so 一 yī becomes yì.

一万wàn (ten thousand)

万 wàn is 4th tone, so 一 yī becomes yí.

一点diǎn (a little)

点 diǎn is 3rd tone, so 一 yī becomes yì.

一台tái ((machines))

台 tái is 2nd tone, so 一 yī becomes yì.

一分fēn (minute / point)

分 fēn is 1st tone, so 一 yī becomes yì.

一本běn ((books))

本 běn is 3rd tone, so 一 yī becomes yì.

一个ge ((general))

个 ge is a light tone that was originally 4th tone, so 一 yī becomes yí.

一杯bēi (cup)

杯 bēi is 1st tone, so 一 yī becomes yì.

一袋dài (bag)

袋 dài is 4th tone, so 一 yī becomes yí.

一直zhí (always)

直 zhí is 2nd tone, so 一 yī becomes yì.

一种zhǒng (kind)

种 zhǒng is 3rd tone, so 一 yī becomes yì.

一份fèn (portion)

份 fèn is 4th tone, so 一 yī becomes yí.

一样yàng (same)

样 yàng is 4th tone, so 一 yī becomes yí.

不要yào (want)

要 yào is 4th tone, so 不 bù becomes bú.

不想xiǎng (want to)

想 xiǎng is 3rd tone, so 不 bù becomes bù.

不可以kěyǐ (may)

可 kě is 3rd tone, so 不 bù becomes bù.

不知道zhīdào (know)

知 zhī is 1st tone, so 不 bù becomes bù.

不懂dǒng (understand)

懂 dǒng is 3rd tone, so 不 bù becomes bù.

不去qù (go)

去 qù is 4th tone, so 不 bù becomes bú.

不来lái (come)

来 lái is 2nd tone, so 不 bù becomes bù.

不睡觉shuìjiào (sleep)

睡 shuì is 4th tone, so 不 bù becomes bú.

不喜欢xǐhuan (like)

喜 xǐ is 3rd tone, so 不 bù becomes bù.

不方便fāngbiàn (convenient)

方 fāng is 1st tone, so 不 bù becomes bù.

不大dà (big)

大 dà is 4th tone, so 不 bù becomes bú.

不小xiǎo (small)

小 xiǎo is 3rd tone, so 不 bù becomes bù.

不长cháng (long)

长 cháng is 2nd tone, so 不 bù becomes bù.

不短duǎn (short)

短 duǎn is 3rd tone, so 不 bù becomes bù.

不胖pàng (fat)

胖 pàng is 4th tone, so 不 bù becomes bú.

不瘦shòu (thin)

瘦 shòu is 4th tone, so 不 bù becomes bú.

不能néng (able to)

能 néng is 2nd tone, so 不 bù becomes bù.

不会huì (can / will)

会 huì is 4th tone, so 不 bù becomes bú.

Related Grammar

→Dates in Chinese(HSK 1) →Telling Time in Chinese(HSK 1)

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