BBC官网英语学习:but和but for的用法区别-By Roger Woodham

"All but two of the boys are coming."Here it means except (for) or apart from and we can substitute these prepositions for but in this sentence. We could also use bar which has the same meaning:

but as conjunction

We usually think of but as a conjuction linking two contrastive sentences or clauses:

In the first five examples, repeated information from the first clause can often be left out in the second clause.

But as preposition

We use but as an alternative to except (for), apart from and bar to introduce the only thing or person that the main part of the sentence does not include. It is often used after words such as everyone, nobody, anything, anywhere, all, no, none, any, every.


In a British court of law, a witness giving evidence is required to take the oath before he gives his testimony. He is required to say the following:

But if he has no religion, he says instead:

Note the useful expressions next but one, last but one.

but for

Note that but for as a preposition has a different meaning from but by itself. We can sometimes use it as an alternative to an
if-clause with a third conditional negative sentence, indicating what might have happened if other things had not happened. Compare the following: