That vs. Which

By Ali Hale

One of our readers, Justin, recently wrote to ask:

When proofreading a peer’s article on the solar system, I realized that she, and I, are unsure of the proper use of “that” and “which” in a sentence. Below is [SIC] two examples of the same sentence, one using “that” and the other “which.”

  • “To our knowledge, it is the only body in the solar system which currently sustains life, although several other bodies are under investigation.”
  • “To our knowledge, it is the only body in the solar system that currently sustains life, although several other bodies are under investigation.”

Which is the correct sentence, and what is the general rule of thumb?

Justin, I’ll give you the answer now, rather than making you read to the end of the whole article: the second version of that sentence, using that is correct.

When To Use “That” and When To Use “Which”

Before I come on to the “that”/”which” rule, just a reminder that “who” should always be used when referring to people.

  • The boy who threw the ball.
  • This is the woman who always wears a black shawl.

When referring to objects, though, the rule for using “that” and “which” correctly is simple:

  • THAT should be used to introduce a restrictive clause.
  • WHICH should be used to introduce a non-restrictive or parenthetical clause.

If that leaves you more confused than when you began this article, read on…

A restrictive clause is one which is essential to the meaning of a sentence – if it’s removed, the meaning of the sentence will change. For example:

  • Chairs that don’t have cushions are uncomfortable to sit on.
  • Card games that involve betting money should not be played in school.
  • To our knowledge, it is the only body in the solar system that currently sustains life…

A non-restrictive clause can be left out without changing the meaning of a sentence. Non-restrictive clauses are either in brackets or have a comma before and after them (or only before them if they come at the end of a sentence):

  • Chairs, which are found in many places of work, are often uncomfortable to sit on.
  • I sat on an uncomfortable chair, which was in my office.

Why You Need to Use “That” or “Which” Correctly

Changing that to which or vice versa can completely change the meaning of a sentence. Consider the following examples:

  • My car that is blue goes very fast.
  • My car, which is blue, goes very fast.

The first sentence uses that – suggesting I own more than one car (and even implying my other cars might not be so fast). This is what happens if we leave out the clause and write:

  • My car that is blue goes very fast.
  • My car goes very fast.

The sentence’s meaning has changed: the reader does not know which one of my cars goes very fast.

However, the sentence using which simply informs the reader that my car is blue. We can take the clause out without losing any essential information:

  • My car, which is blue, goes very fast.
  • My car goes very fast.

“That” and “Which” in Common Usage

It is common today for which to be used with both non-restrictive and restrictive clauses, especially in informal contexts:

  • Who ate the cake that I bought this morning?
  • Who ate the cake which I bought this morning?

The clause “that I bought this morning” is essential to the meaning – I’m not asking about a cake which I bought yesterday, or this afternoon. Therefore, the first example using “that” is the correct one, but many people would not consider the second ungrammatical.

It is, however, incorrect even in informal contexts to use that for a non-restrictive or parenthical clause. For example, these sentences would be considered incorrect:

  • This computer, that I have never liked, is very slow.
  • The blue desk, that my father gave me.

An easy way to watch out for these is to look for instances where you have a comma followed by the word that. If I’d know this years ago, it would have saved me a lot of frustration with Microsoft Word!

Even though the usage of which has been relaxed to some extent, it is still better to keep your writing as clear as possible by using which for only non-restrictive clauses, and that for restrictive ones.

So, to return to Justin’s example:

  • “To our knowledge, it is the only body in the solar system which currently sustains life, although several other bodies are under investigation.”
  • “To our knowledge, it is the only body in the solar system that currently sustains life, although several other bodies are under investigation.”

The second sentence, using that is correct, but many people would consider the first sentence permissible too. In a formal context such as a scientific paper, it is better to use that for total clarity.

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88 Responses to “That vs. Which”

  • Aditya

    Hi,
    Could you please explain why you have used “which” and not “that” in the sentence where you explain a restrictive clause (“A restrictive clause is one WHICH….”). Going by your explanation, it should be “that”. Don’t you think?

  • Ganesh

    Which is the right sentence and why?

    1. A is a subsidiary of B which is in turn a subsidiary of C
    2. A is a subsidiary of B that is in turn a subsidiary of C

    Can you help me?

  • Kathy Toy

    I got the overwhelming impression from an English (i.e., British) friend that this is North American usage and what he was taught is not the same. The British seem to use “which” in places where “that” is right according to what you explain and what I learned. My friend, who is normally placid, became very upset and almost angry as I was explaining the usage to him, and I often hear “which” used in this way while watching or listening to British programs.

  • Andrea

    Thanks! This helped me so much! I’m currently studying for the SAT and other websites didn’t clarify what restrictive and nonrestrictive meant, but I’m so glad I stumbled across your website!

  • Reza

    According to your explanation, the below sentence is restrictive, but between “that’ , and “which” , “which” is the correct answer.

    The car to which you are referring happens to to be mine!

    Please clarify.

  • Nana

    RE: Dale A. Wood on March 22, 2013 5:32 pm, who wrote:
    “The moose and the wapiti are the largest members of the deer family, which are found in North America, Europe, and Asia.” …
    There is a basic problem here that is confusing you. The wrong verb has been used. The noun “family” is singular, and this applies doubly to families in zoology and botany.
    The correct sentence is “The moose and the wapiti are the largest members of the deer family, which IS found in North America, Europe, and Asia.”
    Notice that the antecedent of the pronoun “which” is “family”. Since “family” is singular, then “which” must be singular, too.

    ———————–
    Dale,

    “Of the deer family” is a prepositional phrase; it should not determine verb tense. ‘Are’ was correct.

    Alternatively:

    “The moose and the wapiti, which are found in North America, Europe, and Asia, are the largest members of the deer family.”

  • John Rayner

    Kudzu, the [SIC] indicates an error (the one you pointed out) in the original piece sent in by Justin, one of this site’s readers.

  • Cathy M. Rapp

    Googled the proper usage of “that” vs. “which” and discovered your website. You provided the best and clearest explanation I’ve come across in my many years of being education and working. Thank you. I just shared your link w/ my daughter who is in college.

  • RJ Reuter

    Is it appropriate to use “which” to introduce an essential clause if you have used “that” to introduce a clause previously in a sentence?

    Example: That is a problem which can’t be solved without a lawyer.

  • Ferren MacIntyre

    The easiest way to sort out ‘who’ and ‘whom’ is to think ‘he’ and ‘him’, since we have less trouble with nominative and accusative cases here. The ‘-m’ forms go together. (Even so, care is require when the actor represented by the pronoun changes status in mid stream: ‘I sent the letter to him [accusative object of preposition], who [nominative subject of verb] is the important player.’)

  • Mike Weiner

    @Dale A Wood –

    What if you removed “which are found” completely? So, instead of “The moose and the wapiti are the largest members of the deer family, which are found in North America, Europe, and Asia.”, it would simply read “The moose and the wapiti are the largest members of the deer family in North America, Europe, and Asia.”

    Maybe I’m missing something…but I sure love this article and the comments!

  • Gerry Conetta

    First, your website appears to be an authoritative source of grammatical answers and you are to be commended. Thank you.

    I have a possible mistake to point out to you however. “To our knowledge, it is the only body in the solar system that currently sustains life…” solves the problem of whether to use “that” or “which”. It however misses another major problem. Sustaining life is referring to body rather than solar system and, therefore, the sentence should read, “To our knowledge, it is the only body that currently sustains life in the solar system…”

  • Dale A. Wood

    Sona on July 31, 2009 7:46 am, wrote this:
    Hi,
    Could someone help me out with this sentence:

    1. “The moose and the wapiti are the largest members of the deer family, which are found in North America, Europe, and Asia.”

    2. “The moose and the wapiti are the largest members of the deer family that are found in North America, Europe, and Asia.”
    [This sentence is incorrect on several different foundations.]

    There is a basic problem here that is confusing you. The wrong verb has been used. The noun “family” is singular, and this applies doubly to families in zoology and botany.

    The correct sentence is “The moose and the wapiti are the largest members of the deer family, which IS found in North America, Europe, and Asia.”
    Notice that the antecedent of the pronoun “which” is “family”. Since “family” is singular, then “which” must be singular, too.

    The relative pronoun “which” is one that can be either singular or plural, depending on the antecedent, and this applies also to the pronouns “you”, “who”, and “what”.

    These pronouns are strictly singular {I, me, he, him, her, hers, it}.
    These pronouns are strictly plural {we, us, they, them}.

    The possessive forms of all of the pronouns above, except one, are straightforward. This is “which”, and its possessive form is “whose”.
    This is just the same in German, in which the possessive pronoun is “wessen”.

  • Warsaw Will

    @Charles – I think it was Fowler who first put it forward as a suggestion and it has been taken up by some but certainly not all authorities, especially in the US. It has since been elevated into a “rule” (as here) which has absolutely no basis in grammar nor usage among the greats of literature. And it is not a rule endorsed in EFL teaching, for instance. You would have thought that now that even Associated Press had dropped their insistence on restrictive “that”, this shibboleth would have been finally put to bed. Incidentally, I doubt Mark Nichol would have been quite so categorical.

    @Paul Giles – I’m in total agreement, except that not all Americans accept these “rules”, either; there is a long discussion on both topics in Merriam-Webster Dictionary of English Usage. It’s all available in Google Books, page 895.

  • Paul Giles

    Here, too, you need to distinguish US from UK usage. In standard UK usage a defining (restrictive) relative clause can start with either ‘that’ or ‘which’ for a thing, and either ‘who’ or ‘that’ for a person.

    A describing (non-restrictive) relative clause starts with either ‘which’ or ‘who’.

    Re. your examples: “My car that is blue goes very fast.” Even as a mistake, this would be a very strange form of words. Wouldn’t the speaker just say: “My blue car”?

    Can’t you put ‘American’ somewhere in the site’s title?

  • Charles

    If common usage allows using “which” for a restrictive clause, who decided (and on what basis and with what authority) to tell other people not to use it restrictively in a formal context?

  • Bob Rager

    To David on May 30th, 2012,

    I’m with you. Take some advice given earlier in the string: 1) Use ‘that’ as your default. 2) Do a ‘which’ hunt. You probably overuse ‘which’ and will usually know if it sounds ‘wrong’.

    Good luck with that!

  • David

    I must admit that even after reading the explanation about when to use which or that, I simply cannot grasp th difference. Is there anywhere else this is explained for those who are not grasping this? Thanks. 🙂

  • San

    I don’t know if a similar example has already been discussed. I often find it difficult to use ‘that’ in sentences like this:

    There were several steps in the processes that need to be performed.

    I believe it should be ‘which’ in this case. Otherwise, it sounds like I need to perform the processes not the steps. I don’t find any examples apart from the use of which vs. that in simpler sentences. Can you help me which one to use and the rationale?

  • MJ Fox

    Dave and Warsaw WIll make excellent points. I find the popular understanding of how to use THAT and WHICH overly simplistic.

  • MJ Fox

    I find the grammar rules for which and that to be problematic when dealing with scholarly articles with long sentences. The examples given when promoting these rules are usually overly simplistic and don’t reflect the realities of writing. Because THAT has other uses as well, it is not difficult to sometimes find sentences with several THATs in it. One can even find whole paragraphs completely littered with THATs – all applied correctly, by the way.

    So while the idea of restrictive and unrestictive clauses is easy to apply to simple sentences, complex theoretical arguments or even just lengthy explanations can in fact result in a rather clumsy collection of far too many properly applied THATs.

  • ItIsSoSadHowMuchGrammarIsOverlookedNowadays—IsAnyoneElseFedUpWithIt?

    @Kat: Yes, it is a spelling rule—arguably the most important. The word (and letter) “I” is unique in that it is the only proper noun which is also a pronoun. Check this fact with whomever you wish—you’ll discover that it is true.
    Therefore, it IS required of you (or anyone else) to capitalize “I” whenever it is used as either a pronoun, or a proper noun—which it almost always is.

    @Damen Stephens: The author of this forum meant not to imply that ONLY the pronoun “who” should be used when referring to people; rather, I believe that he/she meant to imply that, between the two options of “who” versus “that”, “who” is always to be used, for it refers to people.
    Although, if you wish to get technical about it (which almost always pays off), you could also argue that, in a scenario which involves a species other than humankind, it would also be correct to use “who” when speaking of the dominant species—or at least the one being discussed at the moment—, for said species would be the one considered to be the most important.
    For example:
    In the “Redwall” series (a fictional set of stories about mammals and other animals), since there are no humans in them, a sentence would go like the following: “Martin the Warrior was heavily fatigued, after having fought over a dozen evil vermin, WHO wished to attack the peaceable inhabitants of Redwall Abbey.”
    However, most people would prefer to write “that” (or “which”, to some) rather than “who”, for the subject in question is not a human(s).

    @Jean Your comment about the hyphens is both necessary and helpful; however, there is a simpler way to use an “M-dash”, as it is called: Simply hold down the “Alt” key, type in (on the number pad on the right of the keyboard) “0151”, and then release the “Alt” key. The result is called an “Alt code”, for those of you who are unaware. There are many more of them, though this one here is the only one needed for the discussion at hand.
    Also, Jean, you misspelled “hyphen” the last time you typed it. Of course, we all know what you meant; but it is a misspelling nonetheless.

  • Damen Stephens

    It is incorrect to state:

    “just a reminder that “who” should always be used when referring to people.

    “Who” should not always be used when referring to people. “Whom” is sometimes appropriate instead.

  • Warsaw Will

    Sorry, but this is a completely artificial rule, largely popularised by Strunk and White. Foreigners learning English are correctly taught that ‘which’ or ‘that’, and ‘who’ or ‘that’ are all perfectly acceptable in defining (restrictive) relative clauses, but only which and who(m) in non-defining relative clauses.

    The example sentence:

    – My car that is blue goes very fast.

    is also artificial as no native speaker would ever say it. But even if it was, it’s not the use of ‘that’ or ‘which’ that (or which) makes the difference. It’s the use (or not) of commas, or in speech of pauses.

    Jane Austen, for one, used both ‘which’ and ‘that’ in defining relative clauses.

    As for the question as to the use of ‘whom’, most of us simply leave it out altogether, which we can do because it is the object:

    – This the man (who/whom) I love.

  • jim

    “A restrictive clause is one which is essential to the meaning of a sentence. . . .” This is from Mr. Hale’s “That vs. Which” column. I think he’s misused “which” in a column about the proper uses of “that” and “which.” Shouldn’t the quoted sentence read, “A restrictive clause is one that is essential to the meaning of a sentence. . . .”

  • Ganesh

    Great article by the author though I couldn’t understand how to distinguish between restrictive and non-restrictive clauses. The explanation by preciseedit made me understand this clearly.

  • Sharath

    How about this quote:

    “Life is a rainbow which also includes black.”

    I guess, instead of “which”, “that” would have been more appropriate.

  • Dave

    The article is indeed clear and simple. There are several issues though that need to be tended, especially those related to the posts of Peyton Todd on October 19, 2010 and of Steve on April 27, 2011. The comments bring up declarations that the clear-cut rule should not be applied thoughtlessly.

    I would argue that restrictive vs non-restrictive rule is applicable to most simplistic case, namely, when “which” unambiguously introduces less relevant information. In this case, “which” clause should also be separated by commas.

    However, one should not forget that “which” acts also as a disjunctive pronoun, implying that several options of the same object are available. In the cases, provided by Peyton Todd, “which” is properly used because the following clause only describes one of possible options available.
    Moreover, “which” added emphasis to the relative clause, whereas “that” plainly denotes its existence.

    ==
    Thomas Jefferson: There are exactly four restrictive relatives in his Declaration of Independence, all of them using ‘which’, namely:

    1. …the causes which impel them to the separation… [there are causes that do not, but those which impel are related, and we mean it]
    2. such is now the necessity which constrains them to alter their former systems of government…[the necessity dictates many things, but the one which constrains is taken into account]
    3, A Prince whose character is thus marked by every act which may define a Tyrant…[the acts of the Prince are numerous, but those which define a Tyrant are especially stressed]
    4. [so that these colonies have rights] to establish Commerce, and to do all other Acts and Things which Independent States may of right do. [the Independent States can do many unworthy things, but only those which the states may of right do are fought for]

    Charles Darwin:

    “[W]e must acknowledge that man with all his noble qualities, with sympathy which feels for the most debased, but benevolence which extends not only to other men but to the humblist living creature, … still bears in his bodily frame the indelible stamp of his lowly origin.” [the sympathy and benevolence may be directed anywhere, but only one which does in the prescribed way is implied]
    ==

    In this context, I would dare to delve into the subject-article example.

    “To our knowledge, it is the only body in the solar system which currently sustains life, although several other bodies are under investigation.”
    “To our knowledge, it is the only body in the solar system that currently sustains life, although several other bodies are under investigation.”
    “(C)urrently sustains life” is clearly not an irrelevant information, therefore straightforward “, which…” is not an option. Can possibly “which” carry a disjunctive function in the sentence? Can it be reasonably implied that “the only” can be numerous? The answer is no.
    Therefore, once both tests are passed, we safely acquiesce to the latter version, using “that”.

    In conclusion, to my opinion if you have a clear-cut case of irrelevant addition in relative clause, use comma which. Once you have information relevant to the sentence in the relative clause, don’t use commas, and decide whether there is a reasonable choice of options in the clause, or whether you want to stress the information therein.

    I would be infinitely grateful to professional linguists here to confirm my assertions.

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