That vs. Which

By Ali Hale - 3 minute read

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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”

  • Kudzu

    Never mind “which” and “that”. The following is incorrect:

    “Below is two examples of the same sentence, one using “that” and the other “which.””

    It should read “Below are…”

  • Daniel Scocco

    Great stuff Ali.

    I learned a thing or two on this post.

  • bill

    Very good explanation. Thank you. Made up for the skull-splitting “Below is two examples…” 🙂

  • Daniel Scocco

    “Below is two examples” is a quote from the reader, and not a mistake by Ali, the author of the post. I will insert a SIC there.

  • marketeer

    Hmm … but aren’t the following uses of “which” (contained in your own explanation) wrong according to these rules?

    A restrictive clause is one which is essential to the meaning of a sentence …

    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.

  • Nancy

    I have been following your posts on grammar. I do appreciate the opportunity to brush up on this. The usuage of improper grammar has a tendency to jump out at me, thereby distracting me from the point being made. You might consider a post on know vs known.

    If I’d know this years ago,

    Thank you for your very helpful blog.

  • Danica

    Great explanation on “that vs. which”. But I wondered about this sentence:

    “The woman, who none of us ever liked, always wore a black shawl.”

    I thought this sentence would use “whom”. Am I wrong on that? I never could get comfortable with using “who / whom” (among other things), because of the local dialect where I grew up.

  • Ali

    Whoops … thanks, Marketeer! Shows how easy it is to get these wrong (can you tell that the “that”/”which” distinction is one I’ve struggled with over the years?) Clearly I typed too quickly!

    Daniel, if you could edit it to be:

    A restrictive clause is one THAT is essential to the meaning of a sentence …

    The clause “that I bought this morning” is essential to the meaning – I’m not asking about a cake THAT I bought yesterday, or this afternoon.

    … it would spare my blushes. 😉

    Cheers!

    Ali

  • marketeer

    Ali,

    I have also struggled with it. The way that usually works for me is to first try THAT and if it “sounds right,” I go with it. Otherwise, it’s probably WHICH. Obviously this is far from foolproof. My first wake-up call was from a client catching an inappropriate WHICH, which, as you can imagine, was quite embarrassing!

  • PreciseEdit

    Restrictive vs. non-restrictive isn’t actually a question of essential context, though it is related. “Restrictive” means to restrict, or limit, a category, thus indicating one item from all the items in a category. “Non-restrictive” means, well, not being restrictive.

    A restrictive phrase, starting with “that,” of course, is used when more than one thing is in a category and you need to indicate the one to which you are referring. For example, “Read the book that is on the table.” In this case, the catagory of “book” has more than one item, i.e., more than one book, so you need to restrict, or limit, the category to one book. After all, you wouldn’t want to other person to read the wrong book! You want him to read the book THAT is on the table.

    A non-restrictive phrase, starting with “which,” of course, is used when a category only has one item, so you do not need to restrict, or limit, it, though you may wish to provide more information about the thing in question. For example: “Read this book, which is by my favorite author.” Here, “this book” is a categoy of one item, so it does not need restriction. The non-restrictive phrase provides extra information about “this book,” i.e., the author.

    As you note, this is a very common problem, so common, in fact, that we added an article about it in our training manual. It will probably come up on our Perfect Writing Forum, which was recently opened.

  • Kevin

    An error in punctation occurs in the first sentence of the message from Justin; “…I realized that she, and I, are unsure of the proper use…”. The commas are incorrectly inserted after “she” and before “are”. Let us all be correct here. 🙂

  • Sudheer

    @Danica,

    I’m not a grammar expert. Although, I do some spelling and grammar Nazism sometimes. Daniel knows about it. 🙂

    Usage of whom is sparse nowadays. You can simple replace whom with who in most of the places.

    If this topic has not been covered already, I request blog authors to consider for their future posts.

    Thanks to Ali for the great article. Keep them coming.

  • Meg

    “The boy who threw the ball.”

    Isn’t this a sentence fragment?

  • Tarah Sweeney

    Danica, you’re correct. It should be “whom”.

    I remember when to use “whom” when someone “does” something to the object of the sentence.

    In that sentence, the woman is the object and she suffers from being disliked. So you should use “whom”.

    In all other instances you should use “who”. Is that a good explanation?

  • Tarah Sweeney

    @Sudheer and Danica: Please do not think this usage is in decline.

  • Ali

    @Danica: Interesting point. The who/whom distinction is one I struggle with too 😉 I believe that “whom” WOULD be more grammatical in that sentence, but as others have pointed out, it seems to be used less and less…

    I’ll change the example, the last thing I want to do is cause confusion! And perhaps I’ll do some research on the who/whom question for a future article — I think Tarah gives a really good, succinct explanation above.

    Thanks for the comments, all of you. 🙂

    Ali

  • Chris

    Thank you, thank you, thank you for this concise, clear explanation.

  • Noel

    Who/whom as I was taught is a simple choice. “Who” is used as a subject, whom as an object. Example: “It is she to whom I speak.”
    Object of the preposition “to.” “Who is it to whom I speak.” Who with
    a predicate nominative. “Who speaks?” Subject of sentence. There are
    just not as many instances of whom use. (I don’t mind sentence fragmentation.)

  • Danica

    Thank you all for the explanations. I appreciate the way everyone here seems to enjoy language; it’s not something I see very much where I live.

  • Segun Omojola

    hi,
    i was interested in improving my writing skills so i decided to see what the web could offer me and i stumbled on this site. can i tag along and see if i could learn a few things?

    thanks.

  • PreciseEdit

    Since the topic seems to have shifted to “who” vs. “whom”:

    I remember OJ’s lawyer (Johnny Cochran?) saying, “Who is kidding whom?” Well said, OJ-lawyer-guy!

    Actually, since we have had to address this so many times in our work, we’ll probably add it to our training manual–which is to say, if you’re a bit confused by this, don’t worry. You’re not alone.

    This problem, which many people have, is one that is easily corrected with a little understanding and practice.

  • singgih

    oke thanks is this make i understanding in usage word ro speak becouse i was learning speaking english

  • padmavati

    my father owns a car. is the sentence correct?

  • Louis

    The word “permissable” should be spelled “permissible”. The spelling checker was not working?

  • Ali

    Oops, thanks Louis, don’t know how I and the spell checker missed that one! Fixed now.

  • MO

    Can anyone out there help me understand this “A major element of the strategy is simplifying that which is difficult.”

  • Michael

    In terms of logic and set theory, restrictive means a subset: the A that B = the subset of all A’s for which B is also true vs. the set of all A’s, and B is true of all A’s.

    Writing this, I just noticed that I used which for a restrictive clause. I could not find a way to reword it with “that”. It seems that “which” must be used if the relative pronoun is the object of a preposition.

    My bigger question is when to use “that” vs. when to elide it. For example, “the coffee that I made for you yesterday” vs. “the coffee I made for you yesterday.” I tend to “that” too much.

    PS: singgih and Segun Omojola: I know that English is not your native language, but the rule that the pronoun “I” is always capitalized should have been one of the first spelling rules you learned about English. I learned it in the first grade.

  • Michael

    This time I’ll be brief. Kevin, I think the sentence by Justin was correct. He meant “I realized that she is unsure of …, and so I am.” Read aloud, Justin’s sentence would have a pause and change in tone at both of those commas.

  • Kat

    Thanks for the explanation. MS Word keeps correcting my whiches and I wasn’t sure why.

    Though honestly it sounds to me like this is a question of context. To use the blue car example, if my audience knows that I only have one car, then ‘my car that is blue’ is not exclusionary and means exactly the same thing as ‘my car.’

    I think I have been using ‘which’ more often in clauses where I was describing some activity. e.g., I prefer

    ‘the modal window which displays the instructions’

    to

    ‘the modal window that displays the instructions’

    and even after reading this article and realizing why it’s not technically correct….I still think it sounds better. So, where can I petition to get the grammar rules changed ? 🙂

    @Michael I don’t think ordinary grammar rules apply to logic statements including equals signs. And, capitalization is not a spelling rule.

  • Sona

    Hi,
    Could someone help me out with this sentence:

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

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

    First, I was confused whether I should use “that” or “which.” But now that I think about it, they are both wrong. I think the sentence must read “The moose and the wapiti are the largest members of the deer family, AND are found in North America, Europe, and Asia.”
    Why is it that neither “that” nor “which” is correct in this sentence?

  • Sona

    Hi,

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

    At first, I was confused whether to use “that” or “which”. But, now that I think about it, they are both wrong: the usage of a relative pronoun is wrong in the first place. The problem is, I am not able to pinpoint the reason why the usage of a relative pronoun is wrong in this sentence. Could you please help me with this?

  • Sona

    I’m sorry, I posted the same thing (kind of) twice. That’s how desperate I am for the answer! (it was by mistake!)

  • Michael

    @Kat: Sorry for not giving a more normal example. How about this example, which is taken from a page in the US Census website:

    Top Ten Countries with which the U.S. Trades

    I did a web search using “which that you,” because without “you,” you get a lot of hits that use “that” as a demonstrative instead of as a relative pronoun.

    I think it’s a good idea to search the Web for examples, but you’ve got to account for the fact that lots of people make mistakes, esp. in English, which so many people speak as a second language.

    It’s best to limit your data to web sites that can reasonably be expected to be correct. Traditionally, publishers were considered to be authoratative, but lately a lot of newspapers have been very sloppy on their web sites. Try using ‘.edu’ and ignoring pages that were written by students.

  • Rich Higgins

    oh the irony

    “A restrictive clause is one WHICH is essential to the meaning of a sentence”

    SHOULD BE

    “A restrictive clause is one THAT is essential to the meaning of a sentence”

  • Michael McCabe

    A professor corrected a sentence I wrote in this manner:

    Original: The Essenes were another ascetic sect which lived in communities away from…

    Corrected: The Essense were another ascetic sect, ONE which lived in communities away from…

    Is the original stylistically inferior because the relative clause following it is long?

  • Jean

    To Precise Edit, concerning your April 17, 2008 post.
    I teach English Lit and Comp and have noticed a lot of confusion among my students in typing hyphens and dashes. Your hyphens in ‘OJ-lawyer-guy’ are correct. However, your use of ‘manual-which’ uses a hyphen rather than a dash. The problem with this is that readers tend to see it as a compound word rather than your intended setting off of an interjected thought.
    To type a dash, either type ‘space hyphen space’ or ‘hypen hypen.’
    Your reader will then get a longer mark, recognized as a dash, or a space separating the hypen from the surrounding words, also making the mark recognizable as a dash.
    Thanks!

  • Michael

    @Jean: I looked at the source code for this page. “Precise Edit” used an en dash (Unicode 8211 decimal), which is wider than a hyphen. It even looked like an en dash, as in Serbo-Croatian–English Dictionary.

    He’s using it as a break in thought, so he should have used an em dash—Unicode 8212 decimal—instead. In German, an em dash is called a Gedankenstrich (thought dash).

    If your computer does not have an em dash—which means it’s very old–use two dashes instead. If you don’t have a figure dash, use an en dash. They are easy to type on a Mac on all applications: Option-dash for en dash and Shift-Option-dash for em dash.

    Check out the book the “Mac is not a Typewriter.” There is also a PC version of the book.

  • Michael

    BTW, I just realized. This web site’s posting software automatically converts 2 dashes to an en dash, which is what I used between “old” and “use.” The other en and em dashes I typed in directly as Unicode characters.

    I had always thought that 2 dashes meant em dash. I’m not sure if there is a standard convention for this. Here is an attempt at 3 dashes—which I doubt will work.

  • Peyton Todd

    Actually, your that vs. which rule belongs with the rules against splitting an infinitive and ending a sentence with a preposition that ignorant grammarians have foisted upon us for centuries. Yes, ignorant: they either blindly assume the correctness of Latin grammar (in the case of the two rules just mentioned), or notice a tendency but misinterpret it as in the case of your that vs. which rule. A more careful attention to the way good writers use that vs. which would notice that, while it is true that ‘which’, not ‘that’, is required for non-restrictive relative clauses, in the case of restrictive relatives it depends on a more subtle aspect of meaning, namely, whether or not the relative clause reports new vs. old information, a distinction bearing a family resemblance to the restrictive vs. non-restrictive one, but one which is in fact not the same. (The resemblance lies in the fact that non-restrictive relatives tend much more often to contain new information.) Exceptions can be found to this pattern of usage, since most people are not consciously aware of it, newness vs. oldness is a matter of degree, and some people, unfortunately fall for your that vs. which rule. But notice the following, which are just a few of the examples I have collected from good writers:

    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…
    2. such is now the necessity which constrains them to alter their former systems of government…
    3, A Prince whose character is thus marked by every act which may define a Tyrant…
    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.

    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.”

    Please stop foisting your simplistic which vs. that rule upon the general public. Thank you.

  • Jenefer

    Wow this article was fantastic! I read another page before and still didn’t understand the usage. After reading this, it is crystal clear!

    Thank you so much! Very well written!

  • Ashley

    Thank you for this very clear explanation!

  • EnglishMidterm

    Thank you so much! This has helped me for my English midterm! Other websites were so confusing, but this was straight to the point and student friendly. (:

  • waseem

    I was tempted to subsribe for basic english grammar after reading the clarification on that and which.

    Thanks a lot.

  • Vic

    Go on a which hunt. That’s what I do. After I write a book I search for the word “which.” I’m always amazed at how much I overuse it.

  • venqax

    Sona:

    Could someone help me out with this sentence:

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

    That would be

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

    Hope that helps!

    Sorry, I couldn’t resist, LOL. Is it 🙂 or (: ?

  • Jay

    Since this is a grammar site, I thought it appropriate to point out the following sentence: If I’d know (sic) this years ago, it would have saved me a lot of frustration with Microsoft Word!

    Keep up the good work.

  • Michael

    @venqax: The largest of my DEAR family are the ones who eat the least like me, which is another of way of saying that the smallest members of my family are the ones who eat the least.

    Or as a logician would say (and formal logic is often used to clarify structural issues in semantics):

    He really meant and with that and no comma corrected to say: Of all x such that (x is at the same time a member of the deer family and lives in North America, …), moose and wapiti are the largest. I’m sure this is what was meant.

    BTW, that brings up another issue. I used the phrase “in which case.” It seems that this “which” is a relative demonstrative.

  • Michael

    I remember from a linguistics class in college (it was my major) reading the example sentence:

    “Reports the height of the type on the cover of which are mandated by the government should be abolished.”

    Actually, it might have had even more noun phrases before the relative pronoun.

    And to what degree can we use the “extended adjective” (or attributive relative clause) in English, like we do in German?

    Can I say, “The many times around the earth orbiting space ship will land in 2 days.” “The still to be read and voted on budget proposal was 32,578 pages long.”

    And for that English teacher: Can I write without aggravating you: “I don’t want to hire people with that kind-of–sort-of–sounds-like–close-enough-for-government-work way of thinking.”

  • Douglas Dykstra

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

    Or: “The moose and the wapiti are the largest members of the deer family; they’re found in North America, Europe, and Asia.”

  • venqax

    Sorry, my attempted humor, which was sorely lacking, is dearly departed.

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