but
1.许多修辞学书里说句首不可用but，其实句首用but很普通。即使用在一段文字的开首也可以。
2.though ... but ...和although ... but ...都是错误的，该把but改作yet或删去。
3.but ... however不该用，如不该说But that, however, is quite different，该改作But that is quite different或That, however, is quite different。
4.No man but I saw him和No man but me saw him都可以说，意思也相同，现在在文字里用I普通些，在口语里用me普通些。第一句里的but是连接词，第二句里的but是介词。
5.not ... but ...是习语。例如：It is not black, but white.但该注意这习语很容易用错，如说It is not black, but it is white便大错了。
6.not ... but ...是习语，not so much ... as ...也是习语，not so much ... but ...是错误的（英美人往往有这种错误），如I admire him not so much for his learning as for his character（我羡慕他，与其说为了他的学问，不如说为了他的品格）里的as不可改作but。
7.can but和cannot but意思略有不同。can but作“只能”解，如I can but wait是说“我只能等着（没有别的事可以做）”，有时有“至多不过…”的意思，如I can but lose that money是说“我至多失了那笔款子，并不会有其他不幸的事情发生”。cannot but作“不得不”或“不禁”解，如I cannot but think so是说“我不得不这样想”。
can but和cannot but都是比较正式的短语，在口语里通常不用can but而用can only，不用cannot but而用cannot help ...ing或cannot help but。
8.do nothing but或do anything but后面接没有to的不定式，如I could do nothing but wait和I could not do anything but wait。
9.all but perfect是“几乎完美的”，anything but perfect是“极不完美的”。
10.下面每组里的四句意思相同：
- There is no-one here but knows the story.(这里的人都知道这
件事。)
No-one here but knows the story.
There is no-one here but he knows the story.
No-one here but he knows the story. - There are few books but have a misprint or two.(书很少没有两处印刷错误。)
Few books but have a misprint or two.
There are few books but they have a misprint or two.
Few books but they have a misprint or two.
每组里的第一句和第二句里的but是关系代词，第三句和第四句里的but是连接词。
