1：but for(+词) ＝ without ，意为“要不是；如果没有”，意思上相当于一个虚拟条件句。
But for the rain, we would have had a pleasant journey.
# 要不是天下雨，我们这次旅行就惬意了。
But for your help, we couldn't have carried out the plan.
# 如果没有你的帮助，我们不可能实现那个计划。
2：but that（+名） = except that ，意为“若非；要不是”，引导虚拟条件状语从句。
He would have helped me but that he was short of money at that time.
# 要不是他那时候没钱，他会帮助我的。
3：but then = on the other hand ，意为“不过；在另一方面”。
London is a noisy place, but then it's also a place where you get the best entertainment.
伦敦是个闹市，不过它也是能够给你最好娱乐的地方。
4：nothing but = only ，意为“只；不过是”。
We could see nothing but water. 我们只能看见水。
5：not … but …意为“不是……而是……”，连接两个并列的名词、形容词、副词、短语或分句等。
My bag is not black but red.
我的书包不是黑色的而是红色的。
He failed not because he isn't clever but because he didn't work hard.
他失败了，不是因为他不聪明而是因为他工作不努力。
6：no … but 意为“没有……不……”; no but = although 连词, 虽然，尽管。
No child but likes Old Li in our village. 没有孩子不喜欢我们村里的老李。
I can’t marry her, no but we love each other very much. 我不能娶她，尽管我们彼此非常相爱
7：not only … but also … 意为“不但……而且……；既……又……”，连接两个并列成分。
Not only you but also she has to attend the meeting.
不但你而且她也得参加这次会议。
He not only teaches us English but also does other things for us.
他不但教我们英语，而且还为我们干别的事情。
8：not that … but that …意为“不是因为……而是因为……”。
Not that the car is out of order, but that I've not learned to drive.
不是汽车出了故障，而是我还没有学会开车。
9：can’t help but do … 意为“不能不……；忍不住……”。
I can't help but cry.
忍不住哭了，嘤嘤嘤...
10：all but 意为“除……外全都，几乎”。
All but mother in my family can speak English.
除母亲外，我的一家人都会说英语。
His theory is all but correct.
他的理论几乎是正确的。
11：anything but 意为“不见得，决不”。
He is anything but a good headmaster.
不见得是个好校长。
This car is anything but beautiful.
这辆小汽车根本不漂亮。
12：but now 意为“刚刚，适才”。
I saw him in the office but now.
我刚刚看见他在办公室。
I heard the commander talk about you but now.
适才听得司令讲到您。
13：can (or could) but 意为“只能，只好”。
His father can but know a few letters.
他的父亲只能认几个字母。
The old lady could but walk slowly with a stick.
那个老太太只能拄着拐杖慢慢地朝前走。
14：can (or could) not but 意为“不得不，忍不住”。
I could not but tell him about it.
我不得不告诉他这件事。
Seeing her husband's funny face, she could not but laugh.
看见丈夫的滑稽面孔，她忍不住大笑起来。
15：cannot (or could not) choose but 意为“不得不，必须”。
They could not choose but obey.
他们除了服从外别无选择。
16：cannot (or couldn’t) help but不能不, 不得不
I cannot help but be sorry.
我不能不感到遗憾。
17: never … but 意为“每当……就……”。
He never sees Miss Wang but he thinks of his friend, Xiao Ya.
每当见到王女士时，他就想起他的朋友小雅来。
Her brother never comes, but he asks her for money.
她兄弟来时，总是向她要钱。
18：next but one 意为 “再下一个”。
They used to live in the next house but one to me.
他们住在我隔壁的隔壁。
19：no one but 意为“除了……外，谁也不”。
No one but a madman would say such words.
除了疯子，谁也不会说这样的话。
20：not so … (no such a … ) but (that) …意为“没有到（不能……）”。
His English is not so bad but he can make himself understood.
他的英语还不至于差到不能把自己的意思讲清楚的地步。
I'm not so foolish (not such a fool) but (that) I can see what he really meant.
我还没有笨到听不懂他话中的真正含义的地步。
21：first but one (two…) 顺数第二 (三……)
In the brothers Mr. Kong was the first but one.
孔先生在弟兄中排行老二。
22：last but one (two…) 倒数第二 (三……)
We sat in the last row but four. 我们坐在倒数第五排