butconjunction
But joins two ideas and shows that the second one is different from what the first one leads you to expect.
showing a contrastused to join two ideas that are different or that seem not to agree
But usually joins two clauses, with a comma before it, or two adjectives or phrases of the same kind, with no comma. The second part is the one that contrasts with what the first part leads you to expect.
- The room is small but comfortable.
- I called her, but she did not answer.
- He is very rich but not very happy.
- We wanted to go to the beach, but it rained all day.
Synonyms yet; although; though
Compare and (and adds a similar idea; but adds a different one); although; however; yet
starting a replyused at the start of a sentence to show surprise, disagreement, or a change of subject
But at the start of a sentence reacts to what someone has just said or done, or turns the talk to something else. Starting a written sentence with But is correct, though some teachers of formal writing prefer to avoid it.
after an apologyused after a polite phrase, before the thing that you need to say
But here does not show a real contrast. It follows an apology or a polite phrase to make a question, a refusal, or a correction sound softer.
not only ... butused after not only to add a second, often stronger, point
Not only comes before the first point and but, often with also, too, or as well, before the second. When a sentence begins with Not only, the verb comes before the subject: Not only did she win, but she also broke the record.
Usage
But can also mean except (everyone but me) or, in formal English, only (she was but a child). Those uses belong to but as a preposition and as an adverb.