Grammar Which vs. That |
The Blue Book of Grammar and Punctuation

Which vs. That

The which vs. that usage dilemma pops up when working with dependent clauses—also known as subordinate clauses—that require one of these two relative pronouns. A dependent clause contains a subject and a predicate but cannot stand alone as a complete, independent sentence.

Which and that are used with essential (also called restrictive) clauses, which contain information necessary to the meaning of the sentence, and nonessential (nonrestrictive) clauses, which enhance the meaning of the sentence with additional information but are not necessary.

More specifically, which and that are used with a specific type of dependent clause called a relative clause. In this type of clause, the relative pronouns which or that are substituted for the subject or object in the sentence. Identifying this relationship between which and that and the nouns they describe helps us figure out how to use these two relative pronouns.

Which vs. That: The Rules

The first step is to determine whether your dependent relative clause is essential or nonessential to the meaning of the sentence. Does the information have to be there, or does the sentence make sense without it?

You can use this standard rule of thumb to help make your decision: If the dependent clause is essential (restrictive or defining), use that. If the dependent clause is nonessential (nonrestrictive or nondefining), use which.

Another way to check your usage is to imagine a set of parentheses around your which or that clause. If you can remove the information in parentheses and the sentence still makes sense, then you have a nonessential clause and can use which. If you need the information in the parentheses, you have an essential clause that requires that.


Essential: Dogs that perform tricks receive treats.

In this sentence, “that perform tricks” is necessary to define the specific group of dogs that receive treats.

Nonessential: David read the history book, which had a blue cover, for his homework assignment.

In this sentence, “which had a blue cover” provides additional but not necessary information.

Note that the essential clause “that perform tricks” is not set off with commas, but the nonessential phrase “which had a blue cover” is. This is a standard use of punctuation with essential clauses (no commas) and nonessential clauses (commas).

Which vs. That: Are There Really Rules, or Just Preferences?

A contemporary shift in style has resulted in some exceptions to the rules for which and that usage. A writer may make the stylistic decision to use which instead of that as a restrictive pronoun, for example, simply because which sounds better to the ear. Writers who strive for greater precision, however, will follow the defined usage of that as a restrictive pronoun and which as nonrestrictive.

In certain contexts, a writer also may choose to substitute which for that to avoid repetition. For example, a sentence beginning “I read a magazine article that says that…” is correct but clunky. The writer may replace the first that with which (“…article which says that…”), allowing for better sentence flow.

It also is important to keep in mind the multiple functions of that in English. It appears in text so often in so many ways that readers see it and may assume it is an unnecessary or even a “filler” word. But before you strike through that with your metaphorical red pen and replace it with which, first determine whether the information in the dependent clause needs to be there.

Pop Quiz

Using what you understand about which and that, choose the pronoun that is most precise for each sentence. Then determine whether the sentence should contain commas. If so, place the commas in the correct locations in the sentence.

1. Mary said she will buy the car [that / which] has the best fuel efficiency.

2. I’ll take a slice of pizza [that / which] will be my lunch.

3. Wyoming [that / which] was granted statehood in 1890 elected the first female governor pursuant to a special election in the United States.

4. Joe just joined a blues band [that / which] is planning a tour.

5. Our family car [that / which] has a red interior does not get good gas mileage.


Pop Quiz Answers

1. Mary will buy the car that has the best fuel efficiency.

2. I’ll take a slice of pizza, which will be my lunch.

3. Wyoming, which was granted statehood in 1890, elected the first female governor pursuant to a special election in the United States.

4. Joe just joined a blues band that is planning a tour.

5. Our family car, which has a red interior, does not get good gas mileage.


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3 responses to “Which vs. That

  1. Ravi Bedi says:

    The English language pundits can definitely make things easier for users without being too damn rigid. These guys purposely decide to enforce discipline which has long gone out of fashion. There are a lot of things in this otherwise beautiful language that make no sense at all. I’d use “that or which” whichever sounds good to my ears, period.

  2. C. Weis says:

    This is a really great comprehensive explanation.

  3. Kristine says:

    I wish the world could read this. As a writer, I know when to use which/that, but these words are so widely misunderstood! I had a client once who gave me several technical booklets to correct. I corrected hundreds of “whiches.” He fired me because he thought he was right.

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