Chinese Pinyin: Sandhi of the "不" (bù) | Free Online Learning Chinese

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In the Mandarin Chinese Pinyin system, the character '不' (bù) retains its original fourth tone (falling tone) only when it stands alone, is used as part of a word, or appears at the end of a sentence. When '不' precedes another syllable with a specific tone, it undergoes tone sandhi (tone change).

1. '不' Before Fourth Tone

When '不' precedes another fourth tone syllable, its tone changes to a second tone, and the pitch contour shifts from 51 to 35.

Examples:

不必 [need not]：búbì
不便 [inconvenient]：búbiàn
不错 [not bad]：búcuò
不要 [do not]：búyào
不但 [not only]：búdàn
不测 [unforeseen event]：búcè

2. '不' Between Identical Words or Verb and Complement

When '不' is placed between identical verbs or adjectives, or between a verb and its complement, it adopts a neutral tone.

Between identical verbs:

买不买 [to buy or not to buy]：mǎi bu mǎi
去不去 [to go or not to go]：qù bu qù
会不会 [can or cannot]：huì bu huì

Between identical adjectives:

红不红 [red or not red]：hóng bu hóng
大不大 [big or not big]：dà bu dà

Between verb and complement:

看不清 [cannot see/read clearly]：kàn bu qīng
拿不动 [too heavy to carry]：ná bu dòng
打不开 [cannot open]：dǎ bu kāi

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