不但……而且……
Use 不但……而且…… when one fact isn't enough and you want to pile on a second, stronger one — 'not only X, but also Y.' The second clause should escalate, intensify, or add something more impressive to the first. It's the standard progressive connector in writing and careful speech, and unlike English you usually keep both halves explicit in Chinese.
Structure
不但 [CLAUSE A], 而且 [CLAUSE B]
búdàn... érqiě...
How to Think About It
不但……而且…… is an escalator: clause B has to be a step up from clause A, not just a parallel item. If the second half is just another equal trait, you want 又……又…… instead. Also, both halves must share the same subject (or the subject moves to the front of 不但) — splitting subjects on either side of 而且 breaks the parallelism.
Examples
他不但会说中文，而且说得很好。
Tā búdàn huì shuō Zhōngwén, érqiě shuō de hěn hǎo.
Not only can he speak Chinese, he speaks it very well.
这家餐厅不但便宜，而且很干净。
Zhè jiā cāntīng búdàn piányi, érqiě hěn gānjìng.
Not only is this restaurant cheap, it's also very clean.
她不但聪明，而且非常努力。
Tā búdàn cōngmíng, érqiě fēicháng nǔlì.
Not only is she smart, she's also very hardworking.
Common Mistake
Learners drop 而且 because English often omits 'but also,' producing a half-sentence. Chinese keeps both halves: 不但 needs its 而且 partner to feel complete and progressive.
她不但会说英语，会说中文。
她不但会说英语，而且会说中文。
Don't Confuse With
又……又……
又……又…… lists two parallel traits of equal weight ('both X and Y'). 不但……而且…… needs the second item to escalate beyond the first.
不仅……而且……
Almost identical, just a touch more formal. Use 不仅 in writing and 不但 in speech; the rest of the pattern works the same.
不但……反而……
Swap in 反而 when the second clause is unexpected or contradicts what you'd predict. 而且 adds; 反而 surprises.
Practice
Fill in the blank: 他___但会唱歌，而且会跳舞。
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不
Fill in the blank: 这个手机不但好用，___便宜。
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而且
Arrange: 不但 / 而且 / 漂亮 / 这个公园 / 大 / 很
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这个公园不但大，而且很漂亮。
Translate to Chinese: He not only knows the answer, but also explains it clearly.
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他不但知道答案，而且解释得很清楚。
Write a sentence with 不但……而且…… describing a friend.
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我的朋友不但很幽默，而且非常热心。
Hear It in Real Episodes
This pattern appears in 7 Fluentide episodes:
她不但会说流利的英语，而且中文也说得特别好。
它们不但数量多，而且动作非常复杂。
所以不但对环境好，而且经济上也划算。(So it's not only good for the environment, but also economically worthwhile.)