That vs. Which — The Answer to Which One You Should Use (And Why)

That vs. Which — The Answer to Which One You Should Use (And Why)

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That or which? Which one do you use…and when?

It can get confusing, so much so that often you just chuck one in and hope it was the right choice.

And let’s let you in on a little secret: Usually you can get away with it (at least with non-copy-editor types). That’s because most other people are also a little shaky on the which vs. that concept…plus, nowadays, few people are real sticklers about it any more.

That vs. which — It can be tricky!

It makes sense. Initially that and which were used interchangeably.

Then, in the early 1900s, grammarians, most notably the Fowler brothers, decided there should be a rule about using them “correctly” and not interchangeably, and, well, that was that. (And which was which…)

The rule has now become so ingrained in modern usage that nitpickers and strict grammarians will seize on an errant that or which and think you don’t know how to write properly. (You do, of course. We’re sure of it.) Yes, even though it’s not a true crime against grammar, it’s often treated as one. 

That’s why, instead of just picking one and hoping you nailed it, it helps to know the traditional that vs. which rule that so many people still adhere to. So here goes …

When to use that and when to use which: A definitive guide

Let’s start with a super-truncated version of the rule espoused by the Fowlers and many other grammarians: That and which are both used to connect a clause to a sentence. If the clause is necessary to the sentence, you use that. If it’s not, you use which.

Now for a few more details: You use that and which to connect two different kinds of clauses — essential clauses (aka restrictive, defining, or integrated relative clauses) and nonessential clauses (aka, logically, non-restrictive, non-defining, or supplementary relative clauses). 

Here’s a quick breakdown of what’s what, clause-wise:

An essential clause is a clause that is, as you may have guessed, essential to the meaning of the sentence. It contains vital information about the subject of the sentence. And it’s literally an integral part of the sentence — that is, it isn’t set off by commas. Traditionally, when it’s an essential clause you use a that (or, if it’s a person, a who).

I need to get the car that is in the garage.

The clause “that is in the garage” is essential to the sentence because it tells us exactly which car I need to get. There can be other cars, but I need the specific one that’s in the garage.

A nonessential clause is, yes, not essential to the meaning of the sentence. It adds color material, information that adds texture or detail to the sentence but that isn’t ultimately necessary. It’s set off by commas and can be deleted from the sentence without having any impact on the meaning whatsoever. A nonessential clause gets a which.

I need to get the car, which is in the garage.

In this case, the clause “which is in the garage” is telling us a little more information about the car, but isn’t vital to understanding the sentence …the thrust of which is simply that I need to get the car. 

There are some exceptions to the that vs. which rule!

Needless to say, since it’s English we’re talking about, there are some caveats.

Caveat #1: If there’s already a “that” in the sentence, most writers will follow up with a “which” even if it’s opening an essential clause.

Take William Shakespeare. In Romeo and Juliet, he writes: “That which we call a rose by any other name would smell as sweet.” This is much more euphonious than the clunky (but correct) “That that we call a rose…” And if it’s good enough for Shakespeare, it’s good enough for us. Even the grammarians who wrote the initial “here’s how to use which vs. that” thought there were times the rule could be bent.

Which leads us to caveat #2, a very important point: Nowadays most style guides, usage manuals, and dictionaries agree that, when it comes to that and which, the old rule isn’t the end all and be all anymore. They give us quite a bit of latitude, saying we can eschew the traditional “always use that with essential clauses.” Yes, some copy editors and sticklers might disagree, but they’re fighting a losing battle. The new general rule of thumb is simple, and makes life a bit easier: 

Use which when it’s a nonessential clause…but take your choice of that or which when it’s an essential one. It’s your call — whichever you think works best stylistically.

Yes, the (grammatically pure) times are a-changing. And now, that is that…which is to say, we’re done. 

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Photo via Undrey / Shutterstock 

Filed Under: Craft


  • Nothing wrecks the flow of a sentence as quickly and as thoroughly as the word THAT. It sits in a sentence like a giant boulder in the middle of the road and must be avoided. I will rewrite a sentence as many times as necessary, to avoid having to use THAT, and when I can’t avoid it, I will simply ignore the rule and use WHICH. Better to keep the flow of my sentence than to satisfy those few who feel the distinction is important. I’m OK with THAT when it is the first word in a sentence, otherwise, Ugh!

  • That vs. which is some confusing article, so that often you just chuck one in and hope it was the right choice.

  • when speaking you can use any words. But while writing we should use that or which?

  • Kay says:


  • Ha! We feel your pain, Trish!

  • MIke says:

    “it helps to know the traditional that vs. which rule that so many people still adhere to.” Are you saying “that so many people still adhere to.” is an essential clause?

  • Well, this is one copyeditor that believes this rule is one which can pass into history.

    I mean, this is one copyeditor who believe this rule one that can pass into …

    This is one copyeditor …

    That’s it. I’m going on vacation.

    Trish O’Connor
    Epiclesis Consulting LLC

  • Wendy says:

    Actually, that Caveat #1 is illustrating a more general grammar rule: Avoid repeating the same word with a different meaning in the same sentence. In the Shakespeare quote, the initial “that” is working as a pronoun, while the second “that” (if it had been used) would be a conjunction.

  • Wendy says:

    Interesting timing on this. I’ve been mTurking this requester that wants turkers to “explain a story” (I think it’s the “new math” of reading comprehension–needlessly convoluted): if you need to add an explainer to the “subject” or “object” fields, you automatically get a “that _____” to fill in.

    Wonder if I should tell the requester it should be “which”? (Being that this is for language instruction and all.)

  • Vivienne says:

    I would like to sat that you have made things much clearer. Sort of. English, being English, has to come up with exceptions to the rule, though, doesn’t it?

  • I had no idea about the history of ‘that’ and ‘which’. So interesting, thanks for sharing!

  • I’m a “who” user for people and pets too — and, although I can’t remember my using it with aliens, I would if it arose!

    That said, everything has gotten so much laxer; now you can get away with thatting when we’ve always who-ed. (We actually did a podcast episode on this and other “rules” that have fallen by the wayside — )

  • Thanks, Kathryn. And now on to the that vs who debate.

    The boys that ate the cake.
    The boys who ate the cake.

    I always use who with people, aliens, and pets.

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