A 不是 B，是 C — 'not A but B' contrast structure
Reach for this in everyday speech when you want to correct one impression and supply the right one: 'It's not B, it's C.' It's the conversational cousin of 不是...而是... — same job (negate, then replace), but stripped down to bare 是 instead of 而是. Useful for snappy corrections, casual clarifications, and any moment you'd say 'no, actually' in English.
Structure
[A] 不是 [B]，是 [C]
bú shì... shì...
How to Think About It
Two halves doing one job. The first 不是 wipes the slate; the second 是 writes the answer. Because the subject usually carries over, Chinese drops it in the second half — '它算出来的，不是想出来的' has no subject in front of 不是 because '它' is still doing the work. That dropped subject is what makes this version feel light and spoken; reintroduce it and you're back in formal territory.
Examples
这不是茶，是咖啡。
Zhè bú shì chá, shì kāfēi.
This isn't tea, it's coffee.
他不是我哥哥，是我表哥。
Tā bú shì wǒ gēge, shì wǒ biǎogē.
He isn't my older brother, he's my cousin.
我不是不喜欢，是没时间看。
Wǒ bú shì bù xǐhuan, shì méi shíjiān kàn.
It's not that I don't like it — I just don't have time to watch.
Common Mistake
Beginners stuff a 但是 between the two halves, treating the structure like an English 'not A, but C.' Chinese already encodes the contrast in 不是...是, so 但是 is redundant and makes the sentence sound off. The two halves sit comma-separated, with nothing else gluing them.
这不是水，但是茶。
这不是水，是茶。
Don't Confuse With
不是A，而是B
Formal version with 而是 instead of bare 是. Same meaning, but use it in writing, essays, and news; bare 是 reads more conversational.
不是...就是...
Means 'either A or B' — both are possibilities. Don't swap it in: 不是...是... rejects A entirely, while 不是...就是... keeps A on the table.
是A，不是B
Reversed order — affirmation first, correction second. Used when the positive identification matters more than the negation. The 不是...是... order leads with what's wrong; this one leads with what's right.
Practice
他 ___ 老师，是医生。
Show answer
不是
我不是累， ___ 饿了。
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是
Put in order: [不是 / 是 / 这 / 我的 / 他的 / 包]
Show answer
这不是我的包，是他的。
Translate to Chinese: 'It's not a problem — it's a question.'
Show answer
这不是问题，是疑问。
Write one sentence correcting something someone might assume about your job, hobby, or home, using 不是...是....
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Example answer: 我不是上海人，是北京人。 (I'm not from Shanghai — I'm from Beijing.)
Hear It in Real Episodes
This pattern appears in 1 Fluentide episode: