Knowing when to use a comma before “which” can be tricky.
That’s because the rules can vary depending on the context.
But don’t worry. We’ve broken down the most common scenarios to help you understand when a comma before “which” is necessary.
When to Use a Comma Before “Which”
Use a comma before “which” when it introduces a non-restrictive clause or when it follows an introductory phrase. Here’s what that means:
In Non-Restrictive Clauses
A non-restrictive clause adds extra information to a sentence but isn’t essential to the sentence’s core meaning. These clauses are set off by commas.
For example:
- The book, which was published last year, became an instant bestseller.
- The car, which was parked illegally, was towed away.
In these examples, the clauses “which was published last year” and “which was parked illegally” provide additional information but aren’t necessary for the sentence to make sense.
After Introductory Phrases
Sometimes, “which” can follow an introductory phrase. In these cases, you also use a comma before “which.”
For example:
- After the meeting, which lasted two hours, we went for lunch.
- Due to the rain, which was unexpected, the event was canceled.
Here, the introductory phrases “after the meeting” and “due to the rain” are separated from the main clause by a comma before “which.”
When Not to Use a Comma Before “Which”
Don’t use a comma before “which” in restrictive clauses or when it’s part of a prepositional phrase.
In Restrictive Clauses
A restrictive clause is essential to the meaning of the sentence. It provides crucial information that defines or limits the subject of the sentence.
For example:
- The book which you lent me was fascinating.
- The car which is parked outside belongs to my neighbor.
In these sentences, the clauses “which you lent me” and “which is parked outside” are essential to understanding which book or car is being referred to. Therefore, no comma is used.
In Prepositional Phrases
When “which” is part of a prepositional phrase, don’t use a comma.
For example:
- The project on which we are working is due next week.
- The table under which the cat is hiding is very old.
In these sentences, “on which” and “under which” are prepositional phrases, so no comma is needed.
Conclusion
Understanding when to use a comma before “which” can enhance your writing clarity and accuracy. Remember these key points:
- Use a comma in non-restrictive clauses and after introductory phrases.
- Don’t use a comma in restrictive clauses or prepositional phrases.
With practice, applying these rules will become second nature.