How to Use "That" and "Which" Correctly

Co-authored by Alexander Peterman, MA

Last Updated: March 29, 2019 Approved

It can be hard to know when to use “which” and when to use “that” in a sentence, even if you are a native English speaker. Knowing the difference between a restrictive and non-restrictive clause and when and how to use them can help you learn how to use “which” and “that” correctly.

Part 1

Part 1 of 2:

Distinguishing Between a Restrictive and Non-Restrictive Clause

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Determine what a restrictive clause is. The key to knowing if you need to use “which” or “that” in a sentence is deciding if you need to create a restrictive or non-restrictive clause.
- A restrictive clause is one that sets limits on the subject of the sentence. A restrictive clause also contributes to the meaning of the sentence – the sentence won’t make sense without the restrictive clause.
- For example, the sentence “I like flowers that are purple” has a restrictive clause in it and removing it would change the meaning of the sentence. “That are purple” is the restrictive clause, because without it you would just be telling people that you like flowers in general.^{[1]
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2
Determine what a non-restrictive clause is. A non-restrictive clause adds information to the sentence, but removing it doesn’t change the meaning of the sentence. These are usually separated by commas before and after the clause. They may also be distinguished by dashes or parentheses.
- For example, the sentence, “The car, which is red, was totaled in the accident,” has a non-restrictive clause in it because “which is red” can be removed without changing the sentence’s meaning. The car will still be totaled, whether we know its color or not. “Which is red” is the non-restrictive clause.^{[2]
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Determine if you’re using a restrictive or non-restrictive clause. When you’re trying to figure out if you’re using a restrictive or non-restrictive clause, ask yourself if the clause changes the meaning of the sentence or if it just adds information to it.
- If taking out the clause changes the meaning of the sentence, you’re using a restrictive clause. In the sentence "Jimmy likes apples that are red" taking out "that are red" changes the meaning of the sentence; we might think Jimmy likes all apples and not just the red ones. "That are red" is, therefore, a restrictive clause.
- If taking out the clause doesn’t change the meaning of the sentence, you’re using a non-restrictive clause.^{[3]
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  Research source} In the sentence "Jimmy thinks apples, which grow on trees in his yard, are the best fruit," taking out "which grow on trees in his yard" doesn't change the meaning of the sentence. We still learn that apples are Jimmy's favorite fruit, and therefore "which grow on trees in his yard" is a non-restrictive clause.

Part 2

Part 2 of 2:

Deciding to Use “That” or “Which”

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Use “that” for restrictive clauses. If you determine that omitting the clause changes the meaning of the sentence, you need to use “that” in your sentence.^{[4]
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- For example, in the sentence “I like dogs that are brown,” the clause “that are brown” is crucial to understanding the sentence; it limits what type of dogs you like.
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Use “which” for non-restrictive clauses. If omitting the clause only removes additional information from the sentence, you need to use “which” in your sentence.
- For example, in the sentence “I took the firetruck, which is my niece’s favorite toy, to be fixed,” the clause “which is my niece’s favorite toy” only adds information to the sentence. You’re taking the firetruck to be fixed – the fact that the truck is your niece’s favorite doesn’t change the meaning of the sentence.^{[5]
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Determine where you should place commas. If you’re creating a non-restrictive clause and therefore using “which” in your sentence, the clause should usually be surrounded by commas. In some cases, though, you may also use dashes or parentheses to separate a non-restrictive clause.
- For example, “I love lobster, which is expensive, because it reminds me of growing up by the ocean,” would still have the same meaning without “which is expensive.” Therefore, "which is expensive" is the phrase you should surround with commas.
- If you know you have a non-restrictive clause and need to use “which,” but don’t know where to put the commas, test it. Your sentence should still make sense if you take out the words surrounded by commas.^{[6]
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Community Q&A

Question

How is "which" used in a question?

Community Answer

"Which" is used in a question when you are referring choices or options. Some examples would be "Which flower do you like?" "Which song do you want to play?" "Which store are we going to?"
Question

How do I use "should" and "must" correctly?

Community Answer

"Should" is a suggestion; "must" is an insistence, usually used when something is imperative.
Question

"I was sorry that I could not to go to class." Is this sentence correct?

Donagan

Top Answerer

Almost. "...that I could not go to class."