介词but表示“除……外”，即英语except, other than或not including的意思，是最常用的介词之一。主要用法有以下几点：
①与no, no one, none, nobody, nothing, nowhere等词连用。例如：
No one can do it but him.只有他才能担当此任。/None but him knows this plant.只有他认识这植物。
I heard nothing but the wind.除了风声，我什么也没听到。
②与all, anything, anywhere, every, everybody, everyone等词连用。例如：
You were all wrong but me.除我外，你们都错了。
Everybody arrived on time but yourself.大家都按时到达，就是你自己没有。
Have you ever been to anywhere else but Beijing? 除了北京外你还去过别的地方吗？
③与who, what, where及形容词最高级等连用。例如：
Who but a fool would do such a thing? 除傻瓜外，谁还会干这样的事情？
What is she but my wife? 她不是我的妻子还会是什么呢？
He is the thinnest man in our school but Mr He.除何先生外，他是我们学校里最瘦的人。
④跟名词、代词、数词、形容词、副词、介词短语或名词性从句作宾语。例如：
None but his dog saved him.除了他的狗以外，没有人救了他。
I have written all my letters but one.我只差一封信就写完了。
He felt all but dead with fatigue. 他感到累得要死。
She was anything but mad.她一点也不疯。
I remember I put it nowhere but in desk.我记得我只是把它放在书桌里。
I believe all but what he said.我根本不相信他说的话。
⑤跟带to的不定式作宾语。例如：
She had no choice but to wait.除了等待，她别无选择。
⑥but前的谓语动词是do时，跟省略“to”的不定式作宾语 。例如：
He did nothing but read a novel yesterday.除了看小说，他昨天什么也没干。
What can you do but take back what you said.除了收回你的话外，你还能做什么？
⑦but前的非谓语动词是to do或doing时，but后的不定式的“to”可省略也可不省略。例如：
I had nothing to do but (to) watch TV.除了看电视，我无事可做。
There was nothing left to do but (to) take a rest.没有剩下什么要做的事情，只好休息。
⑧but前的谓语动词或短语动词要求接动名词时，but后应接动名词。例如：
He thinks of nothing but making money.除了赚钱，他什么也不想。
That official was afraid of nothing but eating pork.那位官员只是怕吃猪肉。
He could bear anything but hearing such bad news.他听到这样的坏消息确实会忍受不了。
⑨不能置于句首，也不能与other连用。例如：
Everyone but me was tired. 除了我以外大家都累了。(=Except for me, everyone was tired.)
Mr. An has no girl-friends but her. 除了她外，安先生没有别的女朋友。(=Mr. An has no other girl-friend besides /except her.)
⑩but后的代词，可用主格也可用宾格；但处于主语位置时，用主格代词更显得自然和合符习惯，谓语应与but前的主语一致。例如：
No one but we (us) is able to do it.只有我们能当此任。
Nobody but we (us) knows of it. 除了我们外，没有人知道这事。
You are all wrong but I (me).除我以外，你们都错了。
I told her that I had never loved anyone but her.我告诉她，除她以外我没爱过任何人。
