grammar rules that and which

Get the grammar rules for using that and which.

There’s a lot of confusion about that and which. These two words are often used interchangeably, even though they’re not necessarily interchangeable.

Historically, that and which may have carried the same meaning, and some English dialects may allow for that and which to be swapped without affecting the meaning of a sentence.

However, in American English, the grammar rules offer a distinct difference between the two words. By the time you’re done reading this post, you’ll fully understand the difference between that and which, and you’ll be able to use both words correctly.

That and Which

As with most grammar rules, there are exceptions and exemptions from the standard ways that and which should be used in a sentence. To gain understanding of confusing word pairs, it’s always best to start with the basics. As we look at how to properly use that and which, we’ll focus on simple, standard usage.

That and which can be categorized into several different parts of speech. Both words can function as adjectives and pronouns. Additionally, that can serve as a conjunction and as an adverb. Today, we’re looking at how that and which should be used when they are working as relative pronouns.

Relative Pronouns

From Wikipedia: “A relative pronoun is a pronoun that marks a relative clause within a larger sentence. It is called a relative pronoun because it relates to the word that it modifies.”

Like adjectives and adverbs, relative pronouns modify other words. Adjectives modify nouns:

  • I have a car.
  • I have a red car.

Adverbs modify verbs:

  • I am walking.
  • I am walking quickly.

The main difference between adjectives and adverbs is that adjectives usually modify things (nouns) while adverbs modify actions (verbs). Relative pronouns also modify words, but they often do so as clauses rather than as single, descriptive words. In the examples below, the clauses are italicized.

  • Bring me the bucket.
  • Bring me the bucket that has apples in it.
  • The bucket, which has apples in it, is blue.

The difference between the words that and which and how they are used as relative pronouns depends on whether the clause they belong to is restrictive or nonrestrictive.

Restrictive and Nonrestrictive Clauses

Restrictive Clauses Are Necessary

A restrictive clause is necessary to the meaning of a sentence. For example:

  • I want the bucket that has apples in it.

If you removed the clause “that has apples in it,” the meaning of the sentence would be lost. Nobody would know which bucket the speaker wants. The clause is necessary to the meaning of the sentence and is therefore a restrictive clause. Because it’s a restrictive clause, it should take the relative pronoun that.

Nonrestrictive Clauses are Unnecessary

A nonrestrictive clause is not necessary to the meaning of a sentence. In fact, it can be removed from a sentence without affecting its meaning. For example:

  • The bucket, which is blue, has apples in it.
  • There are apples in the bucket, which is blue.

If you removed the nonrestrictive clause “which is blue,” from either of the sentences above, the meaning of the sentences would not be lost. We’d still know that the bucket has apples in it. Note that in the second example, the nonrestrictive clause adds information about something that has already been identified. Because the clause is unnecessary to the meaning of the sentence, we know it’s a nonrestrictive clause, and therefore should take the relative pronoun which.

  • Use that before a restrictive (necessary) clause.
  • Use which before a nonrestrictive (unnecessary) clause.

The Easy Way to Remember the Difference Between That and Which

I Needed That

If you need the clause to maintain a sentence’s meaning, then use that. A quick trick for remembering this grammar rule is the phrase “I needed that.”


Because which is also an interrogative pronoun used to mark questions, it is questionable. You can take it or leave it. It’s not necessary. Think of the word which with a question mark (which?) to remind yourself that if the clause’s presence is questionable and can be removed, then you should use the word which to introduce the clause.

Exceptions and Notes

Here are some exceptions and notes to these rules:

  • Which can be used restrictively when it’s preceded by a preposition. For example, “The bucket in which the apples have been stored is blue.”
  • Which is almost always preceded by a comma, parenthesis, or a dash.
  • In British English, there is little distinction between that and which.

Has this article helped clarify any questions you’ve had about grammar rules? Do you have any other questions about that and which? Do you have any tips to share for remembering how to use these two words? Leave a comment.

Sources (aff links):

10 Core Practices for Better Writing

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