“but”一词是中学英语中的一个重要词汇,为了帮助同学们更好地复习,现将其常见用法归纳如下：
1. 作连词,可以连接两个并列成分或两个并列分句,意为“但是,然而”.如：
He is young but very experienced.
他虽然年轻,但很有经验.
Mary likes classical music, but her husband likes rock music.
玛丽喜欢古典音乐,而她的丈夫却喜欢摇滚乐.
注意：but不能与though/although连用.
2. 作介词,常与nothing, nobody, who, all等连用,意为“除……之外”.如：
We had nothing to do but wait. 除了等待之外,我们一筹莫展.
No one but me saw him. 除了我之外,没人看到他.
3. 作副词,意思接近于only,意为“只不过”.如：
She is but a young girl. 她只不过是一个小女孩儿.
4. 需掌握的一些其他用法：
1）用于表示歉意的话语后,引起一个分句,but本身无意义.如：
I’m sorry, but I think you are wrong when you say she did it willingly.
抱歉,你说她情愿做那件事,我觉得你搞错了.
Excuse me, but are you Mr. Smith?
对不起,您是史密斯先生吗?
2) 用在否定句后,引起一个分句,but意为“每当……总是……”.如：
It never rains but it pours.
不下则已,一下倾盆；事情总是接踵而至.
I never go past my old school but I think of Mr. Li.
每当我经过母校时,总会想起李老师.
3) but for(后常接名词、代词)或but that...意为“要不是……”,句子（主句）常用虚拟语气. 如：
But for you, we couldn’t have carried out the plan.
要不是你,我们不可能完成那项计划.
John would have helped us but that he was short of money at that time.
要不是约翰当时缺钱,他一定会帮助我们的.
4) not that...but (that)...不是……而是……
Not that I don’t want to go, but that I have no time.
不是我不想去,而是我没时间.
5) all but 除了……都,几乎,差不多
His letter is all but finished. 他的信快写完了.
6) anything but 绝不,远非
He is anything but an honest man. 他绝不是个诚实的人.
除以上谈到的外,我们常见的but的惯用法还有：can not help but do 不能不,只能；not only...but also...不但……而且……,等等.