Grammar GuideCommaShould I use a comma before "which"?

Should I use a comma before "which"?

Should I use a comma before "which"?

To understand if you should use a comma before which we need to understand the difference between a restrictive and a non-restrictive clause.

A restrictive clause is one where its removal would alter the meaning of the sentence. It is necessary for understanding the meaning of the sentence. In the US, many style guides suggest that you should use "that" rather than "which" for restrictive clauses, e.g. The fruit that we bought was tasty.

A non-restrictive clause does not alter the meaning of the sentence. This additional information is used with “which” and a pair of commas placed before and after the clause:

  • Correct: The fruit, which everyone found tasty, was my best idea.
  • Incorrect: The fruit which everyone found tasty was my best idea.
  • Incorrect: The fruit, which everyone found tasty was my best idea.
  • Incorrect: The fruit which everyone found tasty, was my best idea.

"Which" can also appear as part of a prepositional phrase, e.g. The team in which we played was great. When "which" appears in a prepositional phrase, it should not be preceded by a comma. Other examples of which in a prepositional phrase are "on which" and "of which."

  • Correct: The games, the longest of which lasted two hours, were fun.
  • Incorrect: The games, the longest of, which lasted two hours, were fun.
  • Correct: The situation in which we found ourselves was fun.
  • Incorrect: The situation in, which we found ourselves was fun.

Should you use a comma before "which" in an indirect question?

When you're using "which" at the start of an indirect question, it should be preceded by a comma.

  • Correct: I asked, which is the best?
  • Incorrect: I asked which is the best?

This is similar to the rule about using a comma before a quotation as you can imagine the indirect question being surrounded by quotation marks.

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