But

But is a common English word with several related functions, most notably as a coordinating conjunction used to express contrast or exception between two clauses. It can join two independent clauses, as in I wanted to go, but I stayed home, or introduce a contrasting idea within a single sentence, as in If you want to come, you can, but you will have to leave early.

In addition to its coordinating use, but appears in subordinate clauses to signal a counterpoint or concession, and it can function as an adverb in older or more literary English, meaning “only” or “merely,” as in It is but a dream. The phrase but for is a fixed prepositional form meaning “except” or “without,” for example, But for your help, we would have failed.

Etymology traces but to Old English butan meaning “except, without,” from a Germanic origin. Over time it acquired the modern sense of signaling contrast between statements. Today but remains one of the most frequent conjunctions in English, sharing its role with other contrastive words such as yet, however, and although. Its primary usage is to connect clauses and to introduce a counterpoint, with punctuation typically placing a comma before but when joining two independent clauses.

See also conjunction; coordinating conjunction; adverb.