‘Which’ vs. ‘That’: How to Use ‘Which’ and ‘That’ Correctly

“That” and “which” are relative pronouns that appear in many appositives, or phrases used to describe a noun. Grammarians use the following writing tips to distinguish between “that” and “which.”

• “That” usually appears in restrictive clauses. A restrictive clause is one that cannot be removed without changing the meaning of the sentence.
• “Which” usually appears in nonrestrictive clauses. A nonrestrictive clause contains extra information about its subject but is nonessential to the sentence.
• “That” almost always appears in defining clauses. A defining clause contains essential information about the noun it describes.
• “Which” commonly appears in non-defining clauses. A non-defining clause is considered optional because it can be removed without altering the meaning or grammatical function of a sentence. They frequently appear in dependent clauses, bracketed from the rest of the sentence by commas.

The following examples show how “which” can function in a sentence while adhering to proper grammar rules.

1. 1. In a relative clause, supplying additional information: "The tugboat, which was docked all winter, is now back in service."
2. 2. To introduce nonessential clauses: "The store has vanilla ice cream, which is my favorite flavor, and chocolate, which may be my second favorite."
3. 3. In an optional part of a sentence, surrounded by parentheses: "The downtown area (which is filled with beautiful buildings) could be a good spot for the parade."
4. 4. To ask a question: "Which should we cut: the first sentence or the second sentence?"

The following sentences demonstrate the proper usage of “that” in a sentence.

1. 1. In a defining clause that provides essential information: "The chorus was the part of the song that everyone loved."
2. 2. In a restrictive clause that sets the meaning of the sentence: "The car that my mom drives now is more reliable than the car she used to drive."
3. 3. To introduce an adverb: "We didn't play that well."
4. 4. Alongside the word “which” in the predicate of a sentence: "The best type of teaching is that which emotionally engages a student."

Take note that the word “that” cannot function as a preposition. Prepositions—like “after,” “under,” and “from”—describe the relationship between nouns. The word “that” can only modify one noun at a time.’

Use this simple rule of thumb when choosing between the common words “that” and “which.”

• Are you trying to describe a specific noun? If so, use “that.” For example, “The crow that perches outside my window is very loud." One exception to this rule: Use “who” when referring to a person and “that” when referring to an inanimate object or an animal without a name. For example, “The woman who beat the world record for not blinking is from our town.”
• Is your description nonessential to the sentence? If so, “which” is typically the right word. For example, "A crow, which is a member of the corvid family, perched outside my window this morning." The description is not essential to this particular sentence because you could just as easily break it up to read: “A crow perched outside my window this morning. Crows belong to the corvid family.”

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