1. 可是；但是；然而
You use but to introduce something which contrasts with what you have just said, or to introduce something which adds to what you have just said.
e.g. 'You said you'd stay till tomorrow.' — 'I know, Bel, but I think I would rather go back.'...
“你说过你要呆到明天的。”——“我知道，贝尔，但我还是想回去。”
e.g. Place the saucepan over moderate heat until the cider is very hot but not boiling...
把炖锅置于中火上加热，直到苹果酒变得很烫，但不要加热到沸腾。
2. 但是；不过
You use but when you are about to add something further in a discussion or to change the subject.
e.g. They need to recruit more people into the prison service. But another point I'd like to make is that many prisons were built in the nineteenth century.
监狱需要招募更多的工作人员。但我想补充一点，很多监狱都是在19世纪建造的。
3. （用于表示歉意）但是
You use but after you have made an excuse or apologized for what you are just about to say.
e.g. Please excuse me, but there is something I must say...
不好意思，但有些话我必须说。
e.g. I'm sorry, but it's nothing to do with you...
对不起，但是这跟你没关系。
4. （引出下文，表示惊讶、难以置信、拒绝或抗议）但是，可是
You use but to introduce a reply to someone when you want to indicate surprise, disbelief, refusal, or protest.
e.g. 'I don't think I should stay in this house' — 'But why?'...
“我觉得我不应该再呆在这所房子里。”——“可是为什么？”
e.g. 'Somebody wants you on the telephone' — 'But no one knows I'm here!'
“有人打电话找你。”——“可没有人知道我在这里啊！”
5. 除了
But is used to mean 'except'.
e.g. Europe will be represented in all but two of the seven races...
除了两项赛事之外，欧洲在其余5项赛事中都有代表参加。
e.g. He didn't speak anything but Greek...
他只会说希腊语。
6. 仅仅;只;才
But is used to mean 'only'.
e.g. This is but one of the methods used to try and get alcoholics to give up drink.
这只是为让那些酗酒者戒酒所尝试的方法之一。
e.g. ...Napoleon and Marie Antoinette, to name but two who had stayed in the great state rooms.
只提两位在贵宾房住过的人，就是拿破仑和玛丽·安托瓦妮特。
7. 借口；托词
You use buts in expressions like 'no buts' and 'ifs and buts' to refer to reasons someone gives for not doing something, especially when you do not think that they are good reasons.
but
e.g. 'B-b-b-b-but' I stuttered. — 'Never mind the buts,' she ranted...
“但——但——但是”，我结结巴巴地说道。——“别跟我讲那些‘但是’了。”她咆哮道。
e.g. He committed a crime, no ifs or buts about it.
他犯了罪，这是无可争辩的。
8. 不得不；非…不可；必然
You use cannot but ,could not but, and cannot help but when you want to emphasize that you believe something must be true and that there is no possibility of anything else being the case.
e.g. The pistol was positioned where I couldn't help but see it...
手枪放在我抬眼就能看见的地方。
e.g. She could not but congratulate him.
她只能祝贺他。
9. 倘没有；要不是
You use but for to introduce the only factor that causes a particular thing not to happen or not to be completely true.
e.g. ...the small square below, empty but for a delivery van and a clump of palm trees...
下面的小广场空空荡荡,只有一辆送货车和几棵棕榈树
e.g. But for you, they might have given us the slip.
要不是你，我们可能已经被他们甩掉了。
10. （表示与前面说过的话略有矛盾）不过，然而
You use but then or but then again before a remark which slightly contradicts what you have just said.
e.g. My husband spends hours in the bathroom, but then again so do I.
我丈夫常占用浴室好几个小时，不过我也是这样。
11. （表示前述事情并不奇怪）不过，但是
You use but then before a remark which suggests that what you have just said should not be regarded as surprising.
e.g. He was a fine young man, but then so had his father been...
他年轻有为，不过他父亲也曾经是。
e.g. Sonia might not speak the English language well, but then who did?
索尼娅的英语也许说得不好，但谁又说得好呢？
12. all but -> see all
anything but -> see anything
