Comma Before “Which”: Rules and Examples

Use a comma before which to introduce a nonrestrictive clause. Example: Sonny is wearing a large hat, which he bought at the flea market.
Don’t use a comma before which when it’s part of a prepositional phrase, such as in which. Example: She wrote an essay in which she analyzed both books’ themes.
Don’t use a comma before which to introduce direct or indirect questions. Example: Which major is the best fit for me? Example: My parents asked me which dates were best to visit.
Restrictive clauses are usually introduced by that instead of which.
Usually, there’s no comma after which. However, some exceptions apply.

Which is a versatile word. It’s a pronoun and a determiner, and in some instances, it’s both. A pronoun is a short word used in place of a noun to keep the language in a sentence or paragraph from becoming redundant. It’s used after the noun (i.e., the antecedent) is introduced. Here’s an example with the pronoun in bold:

Yasmin and Ramon are taking their vacation next week.

A determiner is a word that’s used before a noun to describe the noun’s quantity or ownership. Here’s an example of a sentence with a determiner:

We ate some bread.

Because it’s so versatile, which shows up in a lot of different kinds of sentences. Sometimes, it needs a comma, and other times, it doesn’t. Read on to learn more about when which needs a comma and when it doesn’t.

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Does which need a comma?

Comma before which in nonrestrictive clauses

Comma before which in restrictive clauses

Comma before which in prepositional phrases

Comma before which in questions

Examples of comma before which in sentences

Do you need a comma after which?

Comma before which FAQs

Does which need a comma?

Whether which needs a comma or not depends on how it’s being used in a sentence. When it’s used with a nonrestrictive clause, the answer is yes. In nearly all other circumstances, the answer is no.

Comma before which in nonrestrictive clauses

A nonrestrictive clause is a clause or phrase that adds nonessential detail about a noun or noun phrase.

Jeff’s new car, which is less than a month old, already started leaking oil.

The sentence above includes a nonrestrictive phrase (in bold). In this sentence, the nonrestrictive clause is also an appositive. When which is used with a nonrestrictive clause or phrase, the whole phrase/clause needs to be preceded by a comma. When it’s an appositive, it often needs to be offset by commas.

Nonrestrictive clauses’ defining characteristic is that the details they add aren’t crucial to their sentences’ meaning. Here’s an example of the same sentence without the nonrestrictive clause:

Jeff’s new car already started leaking oil.

Here are a few more examples of sentences that require a comma before which:

My mother’s house, which is in a nice neighborhood, needs a new coat of paint.

Tom’s second book, which he spent 10 years writing, is now a best seller.

Rob tripped over his shoes, which he had left lying in the middle of the floor.

Everyone loved Robin’s video, which she had filmed in her garage.

Comma before which in restrictive clauses

A restrictive clause is a clause that adds detail about a noun or noun phrase and changes the sentence’s meaning. They are used with one of the following relative pronouns:

that
who
whom
whose

Here’s an example of a restrictive clause in a sentence:

The first person who arrived at the party was Kiara.

“The first person was Kiara” is a grammatically correct but bland sentence. It also doesn’t tell us much.

When do you use which vs. that?

In US English, that is always used with restrictive clauses, while which is used with nonrestrictive clauses. However, in UK English, a restrictive clause may use which. Here is an example of a restrictive clause that uses which:

The family which lives next door is always throwing parties.

In the sentence above, the bolded section is a restrictive phrase. If you remove it, the sentence’s meaning changes: The family is always throwing parties. This sentence could be about any party-loving family.

Now compare it to a sentence that uses which as part of a nonrestrictive clause:

The family, which lives next door, is always throwing parties.

See how the bolded section feels more like bonus detail than crucial information in this second example? Use commas to set off a clause beginning with which when the information in the clause can be removed from the sentence without significantly changing its meaning.

Here’s a tip: If you want to be certain you’re using that and which correctly, use Grammarly. Grammarly helps you write stronger by suggesting helpful changes.

Comma before which in prepositional phrases

A prepositional phrase is a phrase that includes a preposition, its object, and any additional words that modify its object. Which is often used in prepositional phrases, and with these, which is not preceded by a comma.

We heard three speeches, the longest of, which went for an hour.

We heard three speeches, the longest of which went for an hour.

The envelope in, which the letter arrived had no return address.

The envelope in which the letter arrived had no return address.

The platform on, which we built our program is very stable.

The platform on which we built our program is very stable.

Comma before which in questions

Which is also used in questions. In this position, it does not need a comma.

Example of a direct question

Which seat should I take?

Example of an indirect question

She asked her colleagues which day would be best for an all-team meeting.

Examples of comma before which in sentences

As we discussed earlier, which is preceded by a comma when it’s part of a nonrestrictive clause. Here are a few examples:

The salad costs $15, which isn’t expensive compared to the rest of the menu.

My jacket, which is red, is hanging in the closet.

Do you need a comma after which?

Generally, you don’t need a comma after which. However, there is an exception to this rule: when which is followed by an interrupter.

An interrupter is essentially a side note in a sentence. It adds detail and, like a nonrestrictive clause, can be removed without significantly changing the sentence’s meaning. Here are a few examples of instances where you’d use a comma after which:

I brought a cake, which, after thinking it over again, I decided the group would appreciate.

He wrote a bunch of clues into the manuscript, which, if you knew what to look for, made the mystery a pretty easy one to solve.

Comma before which FAQs

Is there a comma before which?

Whenever which begins a nonrestrictive clause, it is preceded by a comma.

When do you not need a comma before which?

When which follows a preposition as part of a prepositional phrase, when it introduces a direct or indirect question, and when it introduces a restrictive clause in UK English, there is no comma before it.

Can you use a semicolon instead of a comma before which?

No, it is not correct to use a semicolon instead of a comma before which.