but

but1 [ weak bət, strong bʌt ] function word ***

But can be used in the following ways:

As a conjunction (connecting two phrases or clauses):

She's 83 but she still goes swimming every day.

As a way of starting a new sentence and connecting it to the previous sentence:

It was in Cairo that he met Nadia. But that's another story.

As a preposition (followed by a noun):

There's been nothing but trouble since he came.

As an adverb:

We can but hope that things will improve.

1. ) used for introducing a different idea used for joining two ideas or statements when the second one is different from the first one, or seems surprising after the first one:

We're making a lot of progress, but we've still got a long way to go.

Anna's a highly intelligent girl, but she's very lazy.

a simple but effective way of filtering water

What we are about to do is perfectly legal. But please don't discuss it with anyone.

a ) used after a negative for introducing what is true instead:

His death was not a tragedy, but a release from pain and suffering.

2. ) used for changing the subject MAINLY SPOKEN used when you are saying that you should not talk any more about a subject that you have just mentioned:

It was a very complicated operation. But I don't want to bore you with all the details.

There's also the question of how we're going to pay for this, but we can discuss that some other time.

3. ) used in polite questions, requests, and statements SPOKEN used after expressions such as I'm sorry and excuse me to introduce a polite question, request, or statement:

Excuse me, but is there a post office anywhere around here?

I'm sorry, but all our operators are busy at the moment.

4. ) except used especially after words such as nothing, everyone, or anything to mean except :

She does nothing but complain all day long.

There's no alternative but to scrap the whole plan and start again.

I refuse to discuss my medical history with anyone but Dr. Grant.

5. ) used for expressing surprise SPOKEN used when you are replying to someone and expressing surprise, disagreement, or ANNOYANCE:

I've decided to resign. But why?

But you promised not to do anything without asking me first.

6. ) only FORMAL only:

We can but guess at the extent of the problem.

Several Japanese companies already operate in the U.S., Nissan, Honda, Fujitsu, to name but a few.

7. ) without something happening FORMAL used after negative statements for saying that something does not happen without something else happening or being true:

I never take a bath but the phone rings or someone knocks at the door.

but for

1. ) except for something:

The work was now complete, but for a final coat of paint.

2. ) used for saying that something would have happened if something else or someone had not prevented it:

Lee would certainly have been the starting quarterback, but for his recent injury.

But for your timely warning, we would have been unaware of the danger.

but then MAINLY SPOKEN

used when you are adding a remark that makes what you have just said seem less surprising:

What a stupid thing to do! But then I've always thought Colin was kind of dumb.

No one ever listens to what I say, but then I'm only the assistant manager.

last/next but one MAINLY BRITISH

in a position that is just before the last one/just after the next one:

My name was last but one on the list.

no doubt/question but that FORMAL

used for emphasizing that something is certain:

There was no doubt but that the poor girl had committed suicide.

=> IF 2

but

but 2 [ bʌt ] noun

no buts

used for telling someone that they must do what you tell them to, and that their reasons for not doing it are not good:

I was going to clean my room, but... No buts, just do it.