Tone Changes of '一' and '不'

1. The Tone Change Rule for '不' (bù)

Let's start with the simpler of the two rules, for the character 不 (bù), which means "not" or "no."

Its original tone is the 4th tone (falling bù). The rule is straightforward:

'不' (bù) changes to a 2nd tone (rising bú) only when it is followed by another 4th tone syllable. In all other cases, it keeps its original 4th tone.

This visual guide breaks it down perfectly.

Let's watch a short video to hear this in action.

To summarize with examples:

• Rule applies (bù + 4th tone → bú + 4th tone):

  • 不是 (bù shì) is pronounced bú shì (is not)
  • 不要 (bù yào) is pronounced bú yào (don't want)

• Rule does not apply (bù remains 4th tone):

  • 不吃 (bù chī) - chī is 1st tone (don't eat)
  • 不来 (bù lái) - lái is 2nd tone (don't come)
  • 不好 (bù hǎo) - hǎo is 3rd tone (not good)

As with the 3rd tone rule, remember that Pinyin always shows the original tone. You'll see bù shì, but you need to say bú shì.

2. The Tone Change Rules for '一' (yī)

Next is the character 一 (yī), meaning "one." This one is a bit more complex because it can change in two different ways, or not at all.

Its original tone is the 1st tone (high and level, yī). Here are its rules:

1. When followed by a 4th tone, '一' (yī) changes to a 2nd tone (rising yí).
2. When followed by a 1st, 2nd, or 3rd tone, '一' (yī) changes to a 4th tone (falling yì).
3. It keeps its original 1st tone yī when it's at the end of a phrase, used as an ordinal number (e.g., "first"), or part of a larger number (like in a date or phone number).

This is a lot to take in, so let's use another visual guide. As a visual artist, you might find this flowchart approach helpful for remembering the logic.

Now, let's hear these changes. The same video explains this rule very well.

Let's review the examples:

• Rule 1 (yī + 4th tone → yí + 4th tone):

  • 一个 (yī gè) is pronounced yí gè (one of something; a very common structure)
  • 一定 (yī dìng) is pronounced yí dìng (definitely)

• Rule 2 (yī + 1st/2nd/3rd tone → yì + other tone):

  • 一天 (yī tiān) is pronounced yì tiān (one day) - tiān is 1st tone.
  • 一直 (yī zhí) is pronounced yì zhí (straight; continuously) - zhí is 2nd tone.
  • 一起 (yī qǐ) is pronounced yì qǐ (together) - qǐ is 3rd tone.

• Rule 3 (yī remains 1st tone):

  • 第一 (dì yī) - "the first." Here, yī is an ordinal number.
  • 星期一 (xīngqī yī) - "Monday." yī means "one" in the "day one of the week" context.
  • 十一 (shí yī) - "eleven." yī is the final sound, so it keeps its tone.

3. Practice and Summary

You have now learned the three essential tone sandhi rules of Mandarin. Let's put them all in one place.

Practice Activity:

Your main task now is to internalize these rules so they become automatic. The best way is through listening and repetition.

1. Go back to the two video segments you watched in this lesson.
2. Pause after each example is spoken.
3. Say the phrase out loud yourself, mimicking the pronunciation and the tone change as closely as you can.
4. Do this for each example for both 不 and 一. Try to say them 3-5 times each.

Focus on these key phrases:

• bú shì (不是)
• bù hǎo (不好)
• yí gè (一个)
• yì tiān (一天)
• dì yī (第一)

This active practice is far more valuable than just passively reading the rules.

Conclusion

Congratulations on completing the first module! It was the most technical part of the course, and you've built a solid foundation for everything that comes next. Getting pronunciation right from the start is crucial, and you've now covered all the key components.

Key Takeaways:

• The character 不 (bù) changes from a 4th to a 2nd tone only when followed by another 4th tone (bú shì). Otherwise, it stays a 4th tone.
• The character 一 (yī) is more versatile: it becomes 2nd tone before a 4th (yí gè), 4th tone before a 1st, 2nd, or 3rd (yì qǐ), and stays 1st tone when used as an ordinal number or at the end of a word (dì yī).
• Crucially, Pinyin always shows the original tone. It's your job as the speaker to apply the tone change rules as you read and speak.

Preview of the Next Lesson:
The hard work on abstract sounds is done. It's time to start communicating! In our next lesson, we will begin Module 2 and learn how to use basic greetings and farewells. You'll finally be able to say hello with a perfect ní hǎo and learn other essential phrases like zàijiàn (goodbye).