Even experienced writers struggle with some grammar rules. Knowing whether to use which or that is near the top of that list. Though you may think the two words are interchangeable — surprise! They’re not. We’ll break down the which vs. that debate and give you some examples to help you remember.
- What refers to unlimited options while which refers to limited possibilities.
- What vs. which deals with quantities rather than clauses.
- Deciding whether to use which or that depends on whether it’s used in a defining or non-defining clause.
- Use that in defining clauses that are essential to the sentence.
- Opt for which in non-defining clauses that are not essential to the sentence.
- Use the mnemonic “sandwich crusts aren’t essential” to remember that “which” and nonessentialon-defining clauses go together.
- Commas often offset non-defining clauses.
Which vs. that. They seem like such small, simple words, but there is a right time and place for each. To avoid major grammar embarrassment (just kidding, we don’t judge!), check out our quick guide.
It’s easy to learn when to use which or that and the difference between the two. By the time you finish this article, you’ll be a which vs. that grammar guru.
What is the Difference Between Which and That?
This isn’t about nouns and verbs. Instead, it all comes down to what else is going on in your sentence. The quick answer is that we use that with defining clauses and which to introduce non-defining clauses. To understand things further, we need to get to the root of what those two clauses look like.
Defining vs. Non-Defining Clauses
A defining clause is also known as an essential clause or a restrictive clause. That’s because it adds essential information to the sentence. We’re “restricted” from removing it from the sentence; without it, the meaning would change.
In this example, “that has bad breath” is a defining clause because it’s defining something about the dog. The writer may have several dogs, but he or she is specifically talking about the one that has bad breath. “That” is the right choice in this case.
A non-defining clause is also referred to as a nonessential clause or nonrestrictive clause. It’s not essential to the meaning of the sentence.
Therefore, you could remove it, and your sentence would still mean the same thing. You might lose some fun details or interesting “color” in the process, but the core meaning wouldn’t change.
Tara’s shoes are bright green, whether we know that she bought them on vacation or not. That means “which she bought while on vacation” is a nonrestrictive phrase, and which is the correct word to use.
That or Which: How to Remember the Difference
So, which/sandwich is disposable, meaning nonessential. We use which with nonrestrictive clauses.
On the other hand, that is necessary—that is the part of the sandwich we want to keep!
“That my daughter ate” is important because it explains which sandwich the author is talking about. That means it’s an essential or restrictive clause, so that is the correct word to use.
Which vs. That: How to use Them in a Sentence
There are many ways to use which or that in a sentence. The important thing is to be sure you’re using them correctly. That means sticking to which when you have a nonessential or nonrestrictive clause and using that for essential or restrictive clauses. If you’re not sure whether to use which vs. that, see which type of clause your sentence contains.
In this which vs. that example, we know “that are hybrid” is an essential phrase. Without it, we’d be left with “cars use less fuel,” which has a different meaning. Since “that are hybrid” is a restrictive clause, we’re right to introduce it using that.
While it’s interesting to know where the author found the nail, it’s not essential. If you omit “which was left outside a construction site,” the meaning of the sentence remains. Which is the right choice.
Sometimes you may see that or which paired with another introductory word. The same rules apply even if that or which follows a preposition, such as by, for, or on.
How About What vs. Which?
What vs. which is a whole other ballgame. In general, we use what when we’re referring to an unknown quantity or endless possibilities. We use which when referring to a limited number of items, such as choosing between just two possibilities.
You could’ve eaten anything from pizza to sautéed snails. Using “what” reflects all those possibilities.
That question refers to a limited number of subjects, so “which” is correct.
The same goes for:
You’re looking at the best of a few possible routes, so the possibilities are limited.
Sometimes you can use both what and which in the same sentence, but the meaning will change slightly.
Given the phrasing of the first question, you could answer with any movie in the whole universe. If the author asked you the second question, he or she might be referring to two specific movies.
How do you feel about that vs. which now?