Put a comma before but when it’s used to connect two independent clauses (i.e., two clauses that each contain a subject and a verb).
Put a comma after but only when it is followed by an interrupter (i.e., a parenthetical expression that qualifies the statement or indicates mood or tone).
These rules also apply to using commas with the coordinating conjunctions “and” and “or.”
When to use a comma before but
When “but” is used to connect two independent clauses, it is always preceded by a comma. An independent clause is a clause that has a subject and a verb and can function as a complete sentence.
When the subject of the second clause is a pronoun that refers to the same subject as the first clause, you can omit the pronoun. Doing this eliminates the need for a comma and simplifies your sentence.
When to use a comma after but
A comma should only appear after “but” when it is followed by an interrupter (i.e., a parenthetical expression that adds additional but nonessential information). In these instances, a comma should also appear at the end of the interrupter.
When you don’t need a comma before but
No comma is needed before “but” if it’s connecting an independent clause and a sentence fragment (i.e., a clause that does not contain both a verb and a subject or one that cannot function as a standalone sentence). For example, the clause “If you want” has both a subject (“you”) and a verb (“want”), but it does not express a complete thought.
Quiz: Comma before or after but
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