1
not A but B
用于对照两个选项，否定前者、肯定后者。
He is not a teacher but a doctor.
他不是老师，而是医生。
但是；然而
先理解核心含义，再看它在真实句子里的用法。
但是；然而
Used to introduce a statement that contrasts with or contradicts what has just been said.
He is not a teacher but a doctor.
他不是老师，而是医生。
然而,虽然,尽管,另一方面(引入与先前信念相反或与前述句子对比的从句)
However, although, nevertheless, on the other hand (introducing a clause contrary to prior belief or in contrast with the preceding clause or sentence).
相反,而是(作为常规对立连词,引入与前述否定句或句子对比或矛盾的词或从句)
On the contrary, rather (as a regular adversative conjunction, introducing a word or clause in contrast or contradiction with the preceding negative clause or sentence).
除非(引入限定否定陈述的从句)；也,(古代用法)省略从句主语,作为否定关系词,“除非一个”,“除非这样的”
Except that (introducing a subordinate clause which qualifies a negative statement); also, (archaic) with omission of the subject of the subordinate clause, acting as a negative relative, "except one that", "except such that".
It was raining heavily, but we still went to the park.
雨下得很大，但我们还是去了公园。
I called you twice, but there was no answer.
我给你打了两次电话，但没有人接。
The movie was long, but the ending made it worth watching.
这部电影很长，但结局让它值得一看。
用于对照两个选项，否定前者、肯定后者。
He is not a teacher but a doctor.
他不是老师，而是医生。
连接两个并列成分，表示“不但……而且……”。
She speaks not only English but also French.
她不仅会说英语，还会说法语。
but 作连词连接两个分句，表示转折。
I wanted to go, but I was too tired.
我想去，但是我太累了。
句首用 but 表示与前文对比，较口语化；正式文体中常用 however。
But we still have a lot to do.
但是我们还有很多事要做。
Not this
Although he is rich, but he is not happy.
Use this
Although he is rich, he is not happy.
英语中 although 是从属连词，but 是并列连词，两个不能在同一句里连用；中文“虽然……但是……”的转折在英语里只需保留一个连词，删去 but 后句子结构正确。
Not this
He was tired, but however he finished the work.
Use this
He was tired, but he finished the work.
but 和 however 都表达转折，不能在同一个句子里重复使用；保留 but 作为连词连接两个分句即可，去掉多余的 however。
Focus on the distinctions below. Other candidates are kept compact until a reliable usage note is available.
不但……而且……
She is not only smart but also diligent.
她不仅聪明，而且勤奋。
不过；话又说回来
The hotel was expensive, but then again it was worth it.
这家酒店很贵，但话又说回来，它物有所值。
而是；相反
The issue is not ability but rather attitude.
问题不在于能力，而在于态度。
但还是；然而仍然
It was raining heavily, but still we went for a walk.
雨下得很大，但我们还是出去散步了。
几乎，差一点就
The project was all but finished when the funding ran out.
资金用完时，这个项目几乎就要完成了。
绝不是，一点也不
The trip was anything but boring.
这次旅行一点也不无聊。
仅仅，只有
He wants nothing but the truth.
他只想听到真相。
可是，轻声！那窗户里透出的是什么光？
But I wanted to say goodbye before I left.
但我想在离开前说再见。
但我是一个怪人，我是一个怪胎。
But I never expected the party to end so early.
但我从没料到聚会会这么早结束。
Use but naturally, then get feedback on meaning, tone, grammar, and phrasing.
Revisit a common error or keep this word in your review list.
把but想成一根短木桩，横在句中把前后相反的意思“顶”在一起，所以它表示转折：前句说A，后句却来个“但是”。
语域：neutral 常见场景：日常对话、书面写作、正式演讲 but 作转折连词时，通常适用于所有语体和语境，从日常口语到正式书面语都很自然。相比 however、nevertheless 等词，but 更直接、中性，正式写作中使用也完全可接受。
这些词与 but 同韵，均读 /ʌt/。注意 put /pʊt/ 拼写近似但元音不同。
Dictionary facts from DICTIONARY_API_DEV, ECDICT, WIKTIONARY.