<p><code>bù</code> becomes <code>bú</code> when it precedes a falling tone.</p>

<p>I don't know -> wǒ bù zhī dǎo</p>

<p>I don't do -> wǒ bú zuò</p>

CC BY-SA 4.0
2018-11-25T12:59:42.313Z
2018-11-25T12:59:42.313Z
la Fleur
<p>When I first learned 不，the accompanying pinyin was given as </p>

<blockquote>
  <p>bù (falling tone). </p>
</blockquote>

<p>But I've also been doing Pimsleur Chinese lessons and there is the example </p>

<blockquote>
  <p>wo bú hùi shuo ying wen</p>
</blockquote>

<p>and here 不 is pronounced with a rising tone. </p>

<p>My question is:</p>

<blockquote>
  <p>Is there a rule to when it is bù and when bú? Or does it depend on the speaker's dialect?</p>
</blockquote>

CC BY-SA 4.0
2018-11-25T18:53:21.117Z
phenomenon called tone sandhi, https://eastasiastudent.net/china/mandarin/tone-change-rules/   These rules are **not normally reflected in the tone marks** of pinyin; you just have to know them
user6065
CC BY-SA 4.0
2019-06-16T07:49:46.150Z
Thank you @user6065 that is very helpful information!
user1622
<pronunciation><sandhi>
Can bù (不) change its pronunciation to bú?
# Can bù (不) change its pronunciation to bú?

(Asked by: username_0 on 2018-11-25)

When I first learned 不，the accompanying pinyin was given as

> bù (falling tone).

But I've also been doing Pimsleur Chinese lessons and there is the example

> wo bú hùi shuo ying wen

and here 不 is pronounced with a rising tone.

My question is:

> Is there a rule to when it is bù and when bú? Or does it depend on the speaker's dialect?

**Tags:** pronunciation, sandhi
> **Comments:**
> **username_1**: phenomenon called tone sandhi, https://eastasiastudent.net/china/mandarin/tone-change-rules/   These rules are **not normally reflected in the tone marks** of pinyin; you just have to know them  
> **username_0**: Thank you @user6065 that is very helpful information!  

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## 1 answers

### Answer by username_2 on 2018-11-25. Score: 5

`bù` becomes `bú` when it precedes a falling tone.

I don't know -> wǒ bù zhī dǎo

I don't do -> wǒ bú zuò


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