# Rules of spelling and tone sandhi of “不(bù)”

We will get to know how to write ü after initials. Also learn the right tone of “不” when it is followed by another syllable.

The final “ü” can be used after “j q x n” and “l”. Because “j q x” can not appear before the final “u”, in order to reduce the frequency of writing the two dots of “ü”, we remove them, for example, it is “ü” in “居 jū 曲 qǔ 续 xù”, and if the initial is “n” or “l”, we will keep the original form of “ü”, for example “女 nǚ 绿 lǜ ”.

If there is no initial before “ü”, we use the letter “y” before it, we also remove the two dots, like “雨 yǔ”.

### Sandhi of “不(bù)”

1. When “不（bù）”is followed by a syllable in the first, second or third tone, its tone doesn’t change as in forth tone. Like：不吃 bù chī，不能 bù néng，不好 bù hǎo；不喝 bù hē，不行 bù xíng，不想 bù xiǎng.
2. When “不（bù）”is followed by a syllable in the fourth tone, it changes into the second tone. Like：不是 bú shì, 不会 bú huì .