有老师问：高中《英语》外研版，必修3 Module 4 Grammar 2（p36），but +infinitive 中but 是连词还是介词，教材后面标注是连词，但是教师认为是介词。

说明：

判断but是连词还是介词很简单：

若两个部分可以还原为并列句，则是连词，若不能，则是介词。

教材中的两个例句都可以还原为并列句（词形有相应变化）。

教材呈现的语句都可以还原成并列句：

He does nothing but complain. 还原 He does nothing but he complains.

The workers do nothing but drink tea and talk to each other. 还原 The workers do nothing but they drink tea and talk to each other.

这里的but相当于rather than。

具体可参考以下说明。

根据从用法讲解语言的权威词典Collins English Dictionary 2006版的以下解释，我们可以清楚地看出，do nothing but do或者do not do anything but do里的but是连词，而不是介词：

but

conj

1. contrary to expectation: he cut his hand but didn't cry

2. in contrast; on the contrary: I like seafood but my husband doesn't

3. other than: we can't do anything but wait

4. without it happening: we never go out but it rains

prep

1. except: they saved all but one

2. but for were it not for: but for you, we couldn't have managed

Adverb

only: I can but try, he was but a child

Noun

an objection: ifs and buts [Old English būtan without, except]