That vs. Which: A Guide to Correct Grammar

The difference between “that” and “which” is a common source of confusion for many writers. This article covers the key aspects you need to understand, including the fundamentals of “that” and “which,” when to use each word, and useful tips for proper usage.

That vs. Which: What Is the Difference?

Quick Tips:

• Use “that” in restrictive clauses (no commas), where the information is essential to the sentence.
• Use “which” in non-restrictive clauses (with commas), where the information is extra and non-essential.

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Key Takeaways

When it comes to using which or that as relative pronouns, you should be very careful about which choice you make. While both of them can be used when you’re talking about an inanimate object or an animal that doesn’t have a name, only “that” can be used when you’re talking about a human being.

But how to choose the correct word? Well, according to the American English rules, THAT should be used when you have a restrictive, or an essential clause, while WHICH should be used when the clause is nonrestrictive, or nonessential.

Fundamentals of That and Which

That is commonly used in restrictive clauses—parts of a sentence that are essential to its meaning. Without these clauses, the sentence’s core message would change. Restrictive clauses do not have commas around them. Consider the sentence: “The books that are on the shelf are overdue.” Here, “that are on the shelf” tells us exactly which books we’re talking about—it restricts the subject to only those books.

Which, on the other hand, is used in nonrestrictive clauses. These clauses provide additional, but not essential, information—it can be removed without altering the meaning of a sentence. Nonrestrictive clauses are usually set off with commas. For example: “The books, which have red covers, are overdue.” In this case, “which have red covers” offers extra info and could be omitted: “The books are overdue.”

When to Use That and Which

When to Use That

A restrictive clause is the one that you can’t just get rid of because it’s necessary to understand the meaning of the sentence. It makes the meaning more specific by narrowing a big category to a smaller one. For instance, in the sentence “All visitors that are underaged must be accompanied by their parents”, you can’t cross out the clause. If you do that, the sentence will read, “All visitors must be accompanied by their parents” and this simply wouldn’t make a lot of sense. So, because the clause is essential, you need to use that.

When to Use Which

In contrast, a nonrestrictive clause isn’t necessary. Sure, it gives some additional information but if you don’t use one, your readers will still be able to understand the sentence. For example, you can say, “My house, which is located in Texas, was built fifty years ago”. Even if you don’t specify that your house is in Texas, the meaning of the sentence stays the same. Therefore, the pronoun that you should use is which.

Useful Tips for Using

Note that a restrictive clause doesn’t need commas, while a nonrestrictive clause does. This is one more clue that will help you pick the correct word. These commas are very important because, depending on whether you have them or not, you can change the meaning of the sentence completely. For example, look at these two sentences:

1. The long letter that I received yesterday came from New Zealand.
2. The long letter, which I received yesterday, came from New Zealand.

When the reader sees the first sentence, he will assume that you have many long letters, so you need to specify that you received the one you’re talking about yesterday. It’s possible that a dozen other long letters found you the day before yesterday, last week or last month. This is why you can’t cross out the clause here.

In the second sentence, however, the fact that you received the letter yesterday doesn’t add any essential information. The reader understands that you have only one long letter, and the fact that you received it yesterday doesn’t change anything. If you cross out everything that is in between the commas, the sentence will still make sense.

As the Chicago Manual of Style teaches us, if you have a preposition and need a relative pronoun, you can only use which. For instance, if one of your friends graduated from a very well-known university, the correct way of telling everyone about it would be, “The university from WHICH he graduated is very well-known”.

If you still aren’t a 100% sure about the distinction between that vs. which, there’s no reason to worry because, in fact, these details are only really observed in American English. You’ll often see British writers using either which or that not depending on whether the clause is essential or nonessential but simply because they feel like it.

Still, if you want to follow all the rules, remember that you can throw all the “whiches” out without losing any of the meaning, while all the “thats” should stay in place. If you remember this, you’ll have no problem figuring out when to use each pronoun.

Common Mistakes with That and Which

Using “which” for essential information:

• Incorrect: “The car which I bought last year is blue.”
• Correct: “The car that I bought last year is blue.”
• Explanation: The information is essential to identify which car, so “that” should be used.

Using “that” in non-essential clauses:

• Incorrect: “Her house, that is on the corner, is beautiful.”
• Correct: “Her house, which is on the corner, is beautiful.”
• Explanation: The information about the house being on the corner is non-essential, so “which” is correct.

That vs. Which Examples

Examples of “That” in Sentences

• The book that I borrowed from you is excellent.
• She is looking for the dress that she wore last weekend.
• The test that we took yesterday was very difficult.
• He wants to buy the car that has the best fuel efficiency.
• The cake that she baked for the party was delicious.

Examples of “Which” in Sentences

• The car, which is parked outside, is mine.
• She showed me her new dress, which is blue and white.
• The book, which I read last night, was very interesting.
• He explained the problem, which seemed quite complicated at first.
• The movie, which won several awards, is showing at the local theater.

Examples of Sentences that Use Both “That” and “Which”:

• That is the hotel which we stayed at during our vacation.
• She couldn’t remember the name of the person that called, which was important.
• The painting that hangs in the hall, which is a family heirloom, is over a hundred years old.
• I need to find the report that I was working on, which has to be submitted by tomorrow.
• The team that wins the match, which is the final game of the season, will take home the trophy.

Quiz: Test Your Knowledge

Question 1: Choose the correct word.
The book __ (that/which) is on the table is mine.

Question 2: Fill in the blank.
The car, __ (that/which) I bought last year, is already having issues.

Question 3: True or False.
A restrictive clause limits the meaning of the noun it refers to.

Question 4: Select the right option.
I have a friend __ (that/which) can speak six languages.

Question 5: Identify whether the clause is restrictive or nonrestrictive.
The park, by our house, has a lake. (Restrictive/Nonrestrictive)

Here are hints to guide us:

• If the sentence wouldn’t make sense without the clause, use “that.”
• Commas often accompany “which” since the information is supplementary.