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When is it appropriate to use that as opposed to which?

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I heard a story once about someone copy-editing something by Alfred Tarski. They had switched every occurrence of "that" and "which", since they considered that Tarski had got them completely the wrong way round. Tarski sent back the manuscript with all the occurrences of "that" and "which" swapped back again. – Seamus Sep 6 '10 at 14:12
I am a native speaker and I confess I don't know either; the only time I ever notice it is when using a certain Microsoft product, and I always do what it suggests just to get rid of those damned green squiggles. – Brian Hooper Mar 5 '11 at 11:36
@Brian Hooper: This is precisely why I turn off the grammar checking in Word. I still write however I want, but it bothers me that a software program doesn't approve. I guess that's one definition of neurosis. – Robusto Mar 5 '11 at 12:13
Wish I could up-vote the question twice; this is something that always gets me as well, and I never seem to remember the rules governing the use of the two words. – Will Mar 5 '11 at 12:47
this made me think of, "That which does not kill me makes me stronger" – iamserious Apr 13 '11 at 14:00

10 Answers 10

up vote 47 down vote accepted

That and which are interchangeable when introducing integrated relative clauses. Although some grammar mavens (i.e., people who hold forth on such topics but know little or nothing about linguistics) and copy editors will insist otherwise, the rule is completely bogus.

See, for instance, Language Log on that vs which, written by the co-editor of The Cambridge Grammar of the English Language.

Practically speaking, it is not something that any normal person will generally notice or follow in spoken English and it's frequently — and rightly — ignored even in literary writing. So even from that point of view it's not worth worrying about.

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Three cheers for Language Log! – Vincent McNabb Aug 9 '10 at 2:25
Thanks for the link and the answer. I had been wondering about the distinction some people claim (but I had never learned in English classes), and your answer allowed me to understand the issue better. – Tsuyoshi Ito Dec 9 '10 at 18:32
-1, I hate this answer. There is a difference between that and which in that the latter is nonrestrictive. – Jez Aug 17 '12 at 21:21
@Jez: There is a difference between that and which in that the latter may be used grammatically to mark a nonrestrictive relative clause, and the former may not. In restrictive clauses, of course, both are grammatical. – John Lawler Feb 10 '13 at 17:19
-1 The most useful information here would surely be that that *CAN'T be used in non-defining clauses!!! (you edit it and I'll upvote it!) – Araucaria Jun 14 '14 at 19:29

My answer comes so late that it is probably doomed to dwell at the bottom of the answer column, but the question remains a question about which I care, so my answer adds a point other answers have missed.

"Which" instead of "that" is almost always used in sentences with nonrestrictive qualification, as

The horse, which is in the paddock, is six years old.

The horse would still be six years old even if it were in the stable, see? Alternately and more to the point, there seems to be no second horse in view; there is no four-year-old horse about that might (which might?) also concern us.

As other answers have noted and as NOAD has advised, American English slightly, abstractly prefers the word which—as a conjunctive pronoun—to be reserved for this nonrestrictive use.

However, the best American writers have not uniformly followed NOAD's advice. Peggy Noonan does indeed follow it (with no recent exception I have observed):

My thought, which is really a question, is that candidates for president, while natural competitors, sometimes get to the point where they think they are going to win, and it messes with their heads.

John Steinbeck however does not:

The mattresses which had been on the floor were gone.

Even if you are of the rigid, conservative, antidemocratic school of proper usage, as I tend to be, it is hard to argue with Steinbeck. Nor is Steinbeck the only one.

NOAD's advice, quoted in another answer, is fine as far as it goes. NOAD is correct. NOAD should be heeded. However, there is more to the story than NOAD tells.

The trouble with the conjunctive pronoun that is that that is not just a conjunctive pronoun. It is a word with too many uses for its own good—too many uses, even in this very paragraph. The word that is a word which (a word that?) serves so many roles, in various parts of English speech, that the less frequent word which makes a welcome change. In the usage of which versus that, the euphonic has trumped the strictly logical.

Germanic languages are sometimes like that. Can't help it. It's in the bones of the language. English is not like Greek.

In short, heed NOAD's advice by default, but where which sounds better than that—as in complex sentences it often does, and even sometimes in simple sentences like Steinbeck's—even if you are American, feel free to switch to which.

You may often find cause to switch.

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@sumelic: If you have time, would make the suggested edits? I had not known that all languages are like that. In particular, I had thought that the peculiar usage of "das" and its cognates was a Germanic thing -- unlike, say, "qua," whose cognates are not used in such a way. But my Greek is not so good (as in, my Greek is practically nonexistent), so you may be right. – thb Jan 23 at 16:54
Actually, I think you're totally right about that! I read your comment as more general (about words having multiple grammatical roles) but from what I know this specific case is a feature of Germanic languages. I'll edit in the link I posted, and please check if you like the changes that I make. – sumelic Jan 23 at 16:56
@sumelic: I like the changes, and find nothing further to add to them. You have been generous with your time. Thanks. – thb Jan 23 at 17:25

I have always learned - and therefore taught - that the choice to use "that" or "which" in a restrictive/identifying clause is purely based on register. "That" is used in an informal or spoken setting, whereas "which" is preferably used in more formal situations, for example in a formal report or essay.

"That" and "which" are therefore interchangeable in a restrictive clause, in my book.

Similarly, we can use "that" to refer to a person in informal, spoken register. Here below are examples which are all grammatically correct but go from least to most formal. The last two are probably outdated today.

The guy that I spoke to yesterday was French.

The guy who I spoke to yesterday was French.

The gentleman whom I spoke to yesterday was French.

The gentleman to whom I spoke yesterday was French.

As for usage in non-restrictive clauses, you can only use "which" with commas to mark the non-essential relative clause.

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Register is probably part of it. However, I don't think there's a clear-cut gradient in usage based on register; obviously people who believe restrictive "which" is "grammatically incorrect" will not use it even in formal situations. – sumelic Jan 23 at 16:45

In this particular case, either 'which' or 'that' is grammatical.

In general, 'which' and 'that' are interchangeable when referring to something inanimate.

The main restriction is that that is not usually used to introduce a so-called "non-restrictive relative" (essentially, relative clauses where a pause is obligatory between the relative clause and the surrounding sentence).

However, in your case, the relative clause is of the "restrictive" type and speakers would use either 'that' or 'which' fairly interchangeably.

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At times it seems rather confusing about the appropriate usage of which and that (both are used for groups and/or things and never for person*s*, at least i cant think of any such situation).

I have a simple rule to use them,

'That' implements a Restrictive/Essential clause and 'which' implements a Non-restrictive/Non-essential clause.

In your example, the 1st sentence gives an idea that the particular class of motorcycles are already identified, hence, which begins a non-essential clause.

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There's just one problem with your rule: native speakers don't actually use 'that' and 'which' in this way...! – Neil Coffey May 23 '12 at 8:30
@Downvoters: Do you mind leaving a comment for voting down?!! I don't mind receiving down-votes when my answer is not good enough, it will let the readers get a better information about a subject. That's the reason I wouldn't delete an answer even if it has negative votes. – Fr0zenFyr Feb 4 '14 at 5:31
Reason for downvote (I suspect): Your answer was a duplicate of two previous answers and doesn't actually add anything new. – Peter Shor Apr 10 '14 at 19:55
@PeterShor: I originally answered to this question which was later merged here. I doubt your reason for down-vote, i got a down-vote before it was merged. Thanks for taking time to read my comment. – Fr0zenFyr Apr 14 '14 at 9:33

Actually, there's more to this than the above. The word that is a subordinator; it is not a relative word like who, where, when, or which. Even in integrated relative clauses, they are not always interchangeable. When the relative construction follows a fronted preposition, only relative words will do, so relative pronoun which is available, but that isn't.

We have to protect the environment in which we live.

No art can be properly understood apart from the culture of which it is a part.

Conversely, when the relative clause is post-modifying superlatives, we can choose between that or no subordinator, but which is not possible:

He's the best (that) I've ever seen.

He's the fastest runner (that) I've ever seen.

Also in cleft sentences with prepositional phrases like the following, only that is available.

It wasn't for you that I bought it.

It was from John that she heard the news.

Finally, which usually cannot be used where other relative words would work, but that typically can:

They gave the prize to the girl that spoke first. [who]

He was to leave at the time that she arrived. [when]

They looked every place that she could be. [where]

That's not the reason that she resigned. [why]

I like the way that she plays. [*how]

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A great way to explain the differences; the examples are the best I could ask to clarify the point. – Kris Dec 20 '11 at 14:50
I would say that for the last batch of examples, which would be marginally grammatical though awkward for me—more for some than others. It seems that which can substitute more easily for when, where, and why than for who and how – nohat Jan 24 '12 at 7:17

Well, the difference is slight but real. According to the New Oxford American Dictionary:

In U.S. English, it is usually recommended that which be employed only for nonrestrictive (or nonessential) clauses: : the horse, which is in the paddock, is six years old (the : which clause contains a nonessential fact, noted in passing; the horse would be six years old wherever it was). A : that clause is restrictive (or essential), as it identifies a particular thing: : the horse that is in the paddock is six years old (not any horse, but the one in the paddock).

Note also that the word that can be omitted where it introduces a subordinate clause:

He said he was coming. [He said that he was coming.]

But it is required when it is the subject of the clause:

The family that plays together stays together.

More usage notes from NOAD:

Is there any difference between the use of that and which in sentences such as : any book that gets children reading is worth having, and : any book which gets children reading is worth having? The general rule is that, in restrictive relative clauses, where the relative clause serves to define or restrict the reference to the particular one described, that is the preferred relative pronoun. However, in nonrestrictive relative clauses, where the relative clause serves only to give additional information, which must be used: : this book, which is set in the last century, is very popular with teenagers, but not : this book, that is set in the last century, is very popular with teenagers.

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which of the following would be right? or do they have different meanings? 1. Use the interface that provides access. 2. Use the interface which provides access. – Lea Hayes Jul 26 '11 at 2:49
@Lea: #1 urges you to use whichever interface provides access. #2 says the interface in question does provide access. Also, #2 should have a comma after interface to make clear that you don't mean it in the restrictive, relative sense. – Robusto Sep 10 '11 at 13:35
simplest way for me to remember this is: use "which" to tell that; use "that" to tell which. In other words, use "which" to provide additional (non-essential) information, and use "that" to specify which one. – sgroves Jan 22 '14 at 22:41
It's useful to distinguish British from American usage, here. The OED considers them "equally correct" for restrictive relative clauses oxforddictionaries.com/words/that-or-which. Being an American, I prefer the finer distinctions afforded by the NOAD in this answer. – Reb.Cabin Jul 7 '15 at 16:28
I personally tend to disagree with this answer's conclusion (though I am American), but the conclusion is well argued and well supported. +1 – thb Jan 23 at 14:57

In British English usage the two are largely interchangeable, with the restrictive/non-restrictive distinction being indicated only by the presence or absence of a comma preceding the pronoun in question. This more often manifests itself as a restrictive "which" rather than a non-restrictive "that".

The only dissent that one may encounter in the UK tends to be a result of over-familiarity with the Americanish preferences of the Microsoft Word grammar checker, especially in earlier versions.

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It's not the most authoritative/formal source ever, but the grammar book Woe is I provides an easily remembered rule of thumb that has stuck with me through the years:

"Commas, which cut out the fat, go with which, never with that."

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+1 for Woe is I, which is a great guide to "most grammar issues that still confuse well-educated people". And because I still use this rhyme from it to remember this particular issue. – Jaydles Aug 17 '10 at 2:16
Yikes, that book doesn't know about "singular they"!? books.google.com/… – Mr. Shiny and New 安宇 Sep 24 '10 at 18:27

Generally, "that" goes with restrictive clauses - those where the information provided in the clause is necessary to identify the subject: "The beer that belongs to me" (as opposed to all other beers in the world).

"Which" goes with non-restrictive clauses - those which give information but which do not define the subject: "The beer, which was a little warm, was still tasty."

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+1. But as the Language Log (or any sensible grammar book really) points out, "which" is also acceptable in restrictive clauses: "the beer which belongs to me" is fine. But it's definitely wrong to use "This beer, that was a still warm, was …". – ShreevatsaR Aug 6 '10 at 0:23

protected by RegDwigнt May 19 '11 at 8:22

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