but在句中的用法

but prep. 除了conj. 但是 ad. 仅仅
但; 但是
相关词组:
to have no alternative but
but for = 要不是;如果没有,若非;倘没有
but then = 但另一方面

1 而是; 却是
the plan caused not prosperity but ruin这个计画带来的并非繁荣,
而是没落
2 然而; 但是
She organized her work but accomplished very
little.她安排了她的工作然而
只有一点成效
He is tired but happy. 他虽疲倦但却很高兴
3 除了┅之外
No one but she saw the prowler. 除了她以外, 没有人看到那个小偷
4 要不是; 若非 (用於导引独立子句)
would have resisted but that they lacked courage要不是他们缺乏勇气,
否则
一定会抵抗下去
5 ((口语)) 要不; 要不然
It never rains but it pours.不下雨则已, 一下雨就大雨倾盆
(比喻祸不单行)
6 ((口语)) (常用在否定词之后, 作用同 that)
There is no doubt but right will prevail.无庸置疑地, 正义将会获胜
7 (通常用在否定句或问句之后) 无┅; 而不┅
There never is a tax law presented but someone will oppose
it.只要有税务
的法律被提出, 一定就会有人反对
8 若未┅
"Ten to one but the police have got them." (Charlotte
M.Yonge)如果警察没
有抓到他们, 我就赔你十倍的赌注
9 ((口语)) (同 than) 比┅
They had no sooner arrived but they turned around and
left.他们来的快, 去
得也快
<<介系词>>
除外
<<副词>>
1 仅仅; 不过; 只是
hopes that lasted but a moment 希望仅昙花一现
2 (用以强调的语气)
Get out of here but fast! 马上滚开!
还有：
http://dict.cn/search/?q=but

可以作介词，表示‘除...以外’
e.g.
They
never
meet
but
they
discuss
this
problem.他们每次见面都讨论这个问题。
作连词，表示‘而是,
但是’
e.g.
We
go
to
school
every
day
but
Sunday.我们除了星期日每天都上学。
作副词，表示‘几乎,
仅仅’
e.g.
He's
but
a
boy.他只不过是个孩子。

有转折的意思