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Lesson 29

Tone Changes of 不 (bù)

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Hello and welcome back.

In the last lesson, you learned the crucial negation word 不 (bù) and discovered its fascinating habit of changing its tone in the phrase 不是 (búshì). This phenomenon, known as tone sandhi, is essential for natural-sounding Mandarin. You saw that when 不 (bù) comes before a 4th tone, it changes to a 2nd tone.

Today, we will complete the picture. You will learn the full pronunciation rule for 不 (bù), covering how its tone behaves when followed by any of the four tones. Mastering this will ensure your pronunciation is accurate and fluid as we begin to build more complex sentences.

The Complete Tone Sandhi Rule for 不 (bù)

The rule for 不 (bù) is consistent and relatively simple. Its original tone is the 4th tone (falling), and it only changes in one specific situation.

Here is the entire rule at a glance:

If 不 (bù) is followed by a... The tone of 不 becomes... Written as... Example
1st tone syllable (e.g., chī) 4th tone (no change) bù 不吃 (bù chī) - not eat
2nd tone syllable (e.g., xíng) 4th tone (no change) bù 不行 (bù xíng) - not okay
3rd tone syllable (e.g., hǎo) 4th tone (no change) bù 不好 (bù hǎo) - not good
4th tone syllable (e.g., shì) 2nd tone (changes) bú 不是 (bú shì) - is not

In short: 不 (bù) is always pronounced with the 4th tone, unless it is followed by another 4th tone, in which case it becomes a 2nd tone.

Let's watch a video that breaks this down with clear examples and native audio.

Tone Change Rules for Bu (不) in Mandarin Chinese | Beginner Lesson 15 | HSK 1

This lesson from Harbin Mandarin is dedicated to the tone changes of 不 (bù). It will walk you through both parts of the rule.

Watch from 00:58 to 03:45. The speaker will first cover the cases where 不 (bù) does not change its tone (before 1st, 2nd, and 3rd tones), and then review the case where it does change (before a 4th tone). Mimic the pronunciation of the examples aloud.

Visualizing the Tone Change

To help solidify the rule, let's look at it visually. The following image focuses on the one situation where the tone changes. Remember that in all other cases, it remains a steady 4th tone.

Tone Change Rule for 不 (bù)
This chart clearly shows the pattern: a 4th tone following 不 (bù) triggers the change to a 2nd tone, bú. The examples like 不是 (bú shì) and 不要 (bú yào) are very common phrases.

This next image provides a more technical look at the pitch contour of the tone change, which may appeal to your analytical approach.

Tone Sandhi of 'bù' (不) before a Fourth Tone
This graph illustrates the pitch of the voice. The 4th tone of 'bù' is a high-to-low drop. When followed by another 4th tone, it transforms into a 2nd tone 'bú', which is a rising pitch. This change makes the two consecutive falling tones much easier and more natural to pronounce.

Reading and Practice

Now, let's solidify this with a quick reading exercise and some practice.

The Tone Changes Rules of “不”

The article 'The Tone Changes Rules of “不”' from DigMandarin provides a very clear, text-based summary of the rules.

Please read the first two sections, titled '1. 不 (bù)' and '2. 不 (bú)'. This will serve as a concise review of what you just learned in the video. You can ignore section 3 for now.

Now, test yourself. Based on the rule, what is the correct tone for 不 in each of the following phrases?

  1. 不 + 吃 (chī, 1st tone): to not eat
  2. 不 + 好 (hǎo, 3rd tone): not good
  3. 不 + 看 (kàn, 4th tone): to not look/read
  4. 不 + 行 (xíng, 2nd tone): not okay / not allowed
  5. 不 + 对 (duì, 4th tone): not correct

Check your answers:

  1. bù chī (4th tone, no change)
  2. bù hǎo (4th tone, no change)
  3. bú kàn (2nd tone, changes)
  4. bù xíng (4th tone, no change)
  5. bú duì (2nd tone, changes)

A Glimpse Ahead: The Neutral Tone

There is one other situation where the tone of 不 changes: it becomes a neutral tone when used in a specific question pattern called "verb-不-verb" (e.g., 好不好 hǎo bu hǎo - "is it good?"). We are not learning this structure today, but it's useful for you to know that this third variation exists. We will cover it in detail when we learn how to form this type of question.

Conclusion

Great job focusing on this fundamental aspect of Mandarin pronunciation. Getting tones right is a significant step toward fluency.

Key Takeaways:

  • The character 不 has a base tone, which is the 4th tone (bù).
  • The Rule: When 不 is followed by a syllable with the 1st, 2nd, or 3rd tone, its tone does not change.
  • The Exception: When 不 is followed by a syllable with the 4th tone, its tone changes to the 2nd tone (bú).

You have now fully covered the tone sandhi rules for 不.

Preview of the Next Lesson:
We will now shift our focus from negation back to building new sentence patterns. In the next lesson, you will learn to recognize and write the character 有 (yǒu), which means "to have," and use it to form sentences about possession.