Grammar 6 min read

When Should you put a Comma Before Which?

Main Takeaways:

  • Place a comma before which when which precedes a nonrestrictive clause.
  • A nonrestrictive clause is a phrase that adds non-essential information to a sentence without changing the overall meaning.
  • Don’t place a comma before which when which is part of a prepositional phrase.
  • Don’t use a comma before which when it’s used to pose an indirect question.
  • We use which with nonrestrictive clauses, while we use that with restrictive clauses.
  • When used with a restrictive clause, you don’t need to put a comma before that.
  • Restrictive clauses function as identifiers. Removing a restrictive clause from a sentence changes the sentence’s meaning.

Whether to use a comma before or after which in a sentence is a dilemma that many people face when writing. This grammar guide will teach you when you should and shouldn’t place a comma before which.

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When it comes to grammatical conundrums, commas are often the culprit. Thankfully, learning when to use a comma before and after which is actually pretty easy when you follow several simple rules.

When Should You Use a Comma Before Which?

Simply put, you should use a comma before which when it precedes a nonrestrictive modifying clause. A nonrestrictive modifying clause is a phrase that adds nonessential information to a sentence without altering its meaning. It’s normally set off from the rest of a sentence with commas.
The comma, which can be difficult to use correctly, is Michelle’s least favorite punctuation mark.

In this example, the phrase “which can be difficult to use correctly” is the nonrestrictive modifying clause. It modifies the noun comma, letting us know that commas can be challenging. Without it, however, the primary meaning of the sentence would remain intact.

The comma is Michelle’s least favorite punctuation mark.

In the example above, the sentence is correctly punctuated with a comma before which. Another comma, placed after “correctly,” sets the phrase completely apart from the rest of the sentence. This is typical of nonrestrictive clauses.

Note: Nonrestrictive modifying clauses are also known as nonessential clauses or parenthetical expressions.
Comma before which
Always use a comma before which when “which” precedes a nonrestrictive or non-essential clause.

Should Which Always Be Preceded By a Comma?

The quick answer to this question is no. A comma should always precede which when it introduces a nonrestrictive clause. Otherwise, don’t place a comma prior to which.

There are several other ways that which can be used in a sentence. None of the following ways require a comma before which.

1. When Which Is Used in Prepositional Phrases.

Sometimes which forms part of a prepositional phrase. A prepositional phrase includes a preposition and a noun or pronoun that serves as the object of the preposition. It may also include adjectives that modify the object.

When which appears in prepositional phrases, it’s typically paired with a preposition.

  • in which
  • on which
  • during which
  • after which
  • from which

When used this way, you don’t need a comma before the which.

The platform on which she stood was dangerously high.
The storm during which we lost power was over quickly.
Every evening she had a nightmare in which she was running from a killer clown.
The spaceship from which it came was sleek and gray.
A boy and girl labeled as which and prepositional phrase respectively are staring at each other happily while a heartbroken comma is looking at them. Don't put a comma before which if it's part of a prepositional phrase.
Don’t put a comma before which if it’s part of a prepositional phrase.

2. When Which Forms a Question

Since sentences never begin with commas, it should go without saying that you don’t need one before which when it starts a sentence.

Which comma did you use in your list—the serial comma or the Oxford comma? Oh, wait—they’re the same thing!

After all, it would look pretty strange if it was written as:

, Which comma did you use in your list—the serial comma or the Oxford comma?

There is, however, another potential scenario when which forms a question. That’s the indirect question. In this scenario, a question is implied rather than asked outright. There is no question mark at the end of the sentence in indirect questions (unless they’re embedded in another question).

Direct Question: Which items are on sale?
Indirect Question: I asked the clerk which items were on sale.

Essentially, both examples are asking about what items are on sale. One asks directly, while the other poses the question indirectly.

Comma After Which

Some grammarians believe that a comma can be used after which for reasons of style.

He wrote to the president of the company, which, I might add, was a complete waste of time.

You’ll notice here that by adding a comma after the which, you end up with commas before and after it. This can lead to a choppy sentence. In this case, rephrasing may be the better option.

(rephrased) He wrote to the president of the company. It was a complete waste of time.

That vs. Which: Picking the Right Word

When learning how to punctuate a sentence using the word which, it’s important to understand when which isn’t the right word at all.

One Rule to Guide Them All

It’s easy to get tangled up choosing between that and which, but there’s a simple rule for picking the right word. That is used with restrictive clauses. Which is used with nonrestrictive clauses.

Restrictive Clauses

To simplify, restrictive clauses provide essential descriptive information about the noun they modify. They function as identifiers, essentially narrowing things down. They can’t be removed from a sentence without altering the meaning.
Dogs that are well-trained make better pets.

The restrictive clause in this sentence, “that are well-trained,” modifies the noun—in this case, dogs. This clause narrows it down to a specific category of dogs: well-trained dogs. You can’t remove the clause without altering the sentence’s essential meaning. That makes it a restrictive clause.

When used this way, there’s no need to place a comma before that.

Nonrestrictive Clauses

As discussed earlier, nonrestrictive clauses add non-essential information to a sentence. Unlike a restrictive clause, a nonrestrictive clause doesn’t alter the main meaning of the sentence.
Amy’s dog, which she got from a rescue, was a purebred husky.

The nonrestrictive clause, “which Amy got from a rescue,” adds interesting information and context to the noun, dog. However, you can remove the clause from the sentence without changing the meaning.

No Comma Drama

Punctuating sentences can be challenging, and even experienced writers and grammarians often struggle with proper placement of commas. Remembering simple rules of usage can take the drama out of comma placement, letting the meaning of your sentences come through loud and clear.

Quick Comma Before Which Grammar Quiz

Comma Before Which Question #1

Which statement is incorrect
Correct! Oops! That's incorrect.

The answer is B. You should use a comma before “which” when it precedes a nonrestrictive clause.

Comma Which Question #2

Which sentence is grammatically correct
Correct! Oops! That's incorrect.

The answer is A. "That" is used with restrictive clauses, while "which" is used with nonrestrictive clauses.

Comma Before Which Question #3

Which statement is true?
Correct! Oops! That's incorrect.

The answer is A. Restrictive clauses can't be removed from a sentence without altering the meaning.

Correct! Oops! That's incorrect.

The answer is FALSE. When "which" appears in prepositional phrases, you don't need a comma before the "which."

Comma Before Which
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Read More: How To Use Commas In Your Writing

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Krista Grace Morris

Krista heads up Marketing and Content Creation here at INK. From Linguistics and History to puns and memes, she's interested in the systems we create to share our ideas with each other.

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