Pronunciation Guide
How tone change works for 一 and 不
一 and 不 do not keep the same citation tone in every context. Their spoken tone changes according to what comes next, especially before fourth tones.
How to shape the sound
- Before a fourth tone, 一 usually rises to yí and 不 usually rises to bú.
- Before first, second, or third tones, 一 often falls as yì.
- Practice the whole phrase, not the isolated character, because the sandhi belongs to the chunk.
Common mistakes
- Saying yī gè instead of yí gè.
- Keeping 不 as bù before 是 or 要.
- Memorizing isolated tones without connecting them to phrase context.
Practice with example words
一个 (yí gè)
one (measure word). Because gè is fourth tone, 一 changes to a rising yí in connected speech.
一杯 (yì bēi)
one cup/glass. Before a first tone like bēi, 一 falls as yì rather than staying flat.
一定 (yí dìng)
certainly. The first syllable rises because dìng is fourth tone.
不对 (bú duì)
incorrect; wrong. Say 不对 (bú duì) as a full chunk and let 一 or 不 change tone according to the following syllable.
不好 (bù hǎo)
not good. Say 不好 (bù hǎo) as a full chunk and let 一 or 不 change tone according to the following syllable.
不会 (bú huì)
cannot; won't. Say 不会 (bú huì) as a full chunk and let 一 or 不 change tone according to the following syllable.
Practice with example sentences
我不是。 (wǒ bú shì.)
I am not.. Because shì is fourth tone, 不 changes to bú in the middle of the sentence.
一杯水。 (yì bēi shuǐ.)
A glass of water.. The first syllable falls as yì before the high flat bēi.
不要去。 (bú yào qù.)
Don't go.. Say 不要去。 (bú yào qù.) as a full chunk and let 一 or 不 change tone according to the following syllable.
一个人。 (yí gè rén.)
One person; alone.. Say 一个人。 (yí gè rén.) as a full chunk and let 一 or 不 change tone according to the following syllable.
FAQ
Why does 一 sometimes sound like yí and sometimes yì?
The tone changes to fit the contour of the next syllable and make the phrase easier to say naturally.
Is 不 always bú before a fourth tone?
That is the core pattern in standard Mandarin and the one learners should master first.
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