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Grammarology 2.0: That vs Which

This is the first Grammarology column for 2012. The column will run every few weeks. In the mean time, please, send in your grammar questions. Anything from the trivial to the profound is welcome. Comments are also very encouraged.

Q: Caleb Thompson wrote:

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

AGenerally speaking, that can be used with integrated (restrictive) relative constructions (e.g., This is the one that broke), and which can be used with both integrated (e.g., This is the one which broke) and supplemental (non-restrictive) relatives (e.g., This group, which I’ve taught before, is a nice one).

Of course, as usual, 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. It’s the same that used in content clauses (“noun clauses”; e.g., He said that it was time to go.) This gives it the flexibility you see below. And, as a result, even in integrated relative clauses, that and which 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. (Remember the * means it’s ungrammatical.)

  • We have to protect the environment in which/*that we live.
  • No art can be properly understood apart from the culture of which/*that 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/*which) I’ve ever seen.
  • He’s the fastest runner (that/*which) I’ve ever seen.

Also in cleft sentences like the following where a prepositional phrase is being modified, only that is available.

  • It wasn’t for you that/*which I bought it.
  • It was before I moved here that/*which I met her.

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

  • They gave the prize to the girl that/*which spoke first. [who]
  • He was to leave at the time that/*which she arrived. [when]
  • They looked every place that/*which she could be. [where]
  • That’s not the reason that/*which she resigned. [why]
  • I like the way that/*which she plays. [*how]

As you can see here, if that were a pronoun, it would be a pronoun that replaces not just nouns but almost everything under the rainbow. But if it’s a subordinator, it’s doing exactly what we’d expect.

Bonus material

Merriam-Webster’s Dictionary of English Usage has a good historical overview of the evolution of which and that in relative constructions. They call that a relative pronoun, and historically it may have been so. Now, however, it is a subordinator, as I said above. Other English subordinators include to (e.g., it’s hard to change), for (e.g., it’s hard for me to change), whether/if (e.g., I wonder whether I can change), and how (e.g., I don’t know how I can change).

[Correction added Dec 17, 2012: A previous version of this post erroneously claimed that which was unavailable in all cleft sentences. Thanks to John Anderson for pointing out the error!]

Grammarology 2.0 aims to take the discussion of grammar up a notch or two (your mileage may vary) and should appear about once every few weeks. It’s written by Brett Reynolds, who teaches EAP at Humber College and is just about as nerdy about grammar as you can get. He’s is always happy to take questions, which you can send to

Brett Reynolds teaches English in Humber's EAP program. (OK, who's fooling who with this third-person stuff?) I speak Japanese, remember a fair bit of French, and know something about a few other languages too. I'm crazy about grammar, and spend too much time online for my own good.

Comments (20)

  • Reply Tyson - January 9, 2012

    This is a very immediately useful point, Brett, which I’m sure many grammar teachers are happy to know rules for. Interesting though, I’ve never heard relative clauses referred to as “integrated” before. Restrictive or non, Defining or non, but never “integrated”.

    • Reply Tyson - January 9, 2012

      Oh, that goes for “supplemental” too. 😉

  • Reply Brett - January 9, 2012

    Thanks, Tyson! The problem with “restrictive” is that they aren’t always. The Cambridge Grammar of the English Language gives this example:

    She had two sons she could rely on for help, and hence was not unduly worried

    Here, the clause is integrated into the NP. It’s not supplemental. We can’t just leave it out. But if she only has two sons, in no way is it restrictive. So even though it’s less familiar, I think it’s more useful to think of it this way.

  • Reply Nancy - January 10, 2012

    As a fairly new ESL supply teacher, I love teaching grammar, but I admit, this article has left me extremely befuddled. I’d never heard of cleft sentences or post-modifying superlatives or integrated relative constructions, and I feel like I had been comfortably treading water in a very small pond, but have now found myself dog-paddling in an unfamiliar ocean of grammatical confusion!

    However, with 30 years of Admin Assistant experience under my belt, one skill I have developed is that of proof-reader. There is one teensy little error in one of your paragraphs that came under my radar. I’ve capitalized the word in question.

    “As you can see here, if that were a pronoun, it would be a pronoun THE replaces not just nouns but almost everything under the rainbow. But if it’s a subordinator, it’s doing exactly what we’d expect.”


    A tiny typo, but it adds a little confusion to an otherwise already overwhelming work.

    • Reply Brett - January 11, 2012

      Hi, Nancy, and thanks for the proofread! Fixed now.

      There’s nothing wrong with a bit befuddlement, as long as it’s not overwhelming. If you look at the examples, can you puzzle out one or two of the terms?

      • Reply Nancy - January 11, 2012

        Ohhhh, “puzzle out” isn’t exactly the word. It’s more like “climbing Mt. Everest”. What I’ve realized is that, although I’ve always loved the study and teaching of grammar, I have miles to go before I can consider myself a good teacher. Your article just reminds me of that.

        • Reply Tyson - January 12, 2012

          Being a good teacher isn’t determined by the amount of deep grammar understanding you have, Nancy. How you teach should be more functional than technical. This column is largely for people with a particular interest in the technical aspects of grammar, not a guide by which to teach.

          • Brett - January 15, 2012

            What Tyson said: being a good teacher doesn’t stand or fall on your knowing lots about grammar.

            There are a few terms here that you don’t know, but it’s not insurmountable. What, for example, do you think it would mean to post-modify something?

          • Nancy - January 15, 2012

            I have to reply on Tyson’s post because I can’t see a “reply” to click on, on Brett’s post. But I have to say with sadness that I had to google “post-modifier”. Once I read the description, it made sense to me, but it saddened me to have to google something I should already know!

      • Reply Brett - January 15, 2012

        @Nancy: Who’s to say you should already know it. I have to look up grammar stuff all the time, and I’ve been in this game for 20 years.

        • Reply Tyson - January 16, 2012

          Yes, @Nancy, give yourself a break! =) I’d venture to say that the majority of ELT teachers don’t know the meta-language of the grammar they teach that deeply.

          • Nancy - January 16, 2012

            Well, I do feel a little better, thank you! I still feel intimidated by what I don’t know, but it’s nice to know I’m not the only overwhelmed fish swimming in this complicated ocean!

          • Brett - January 16, 2012

            Maybe you have a question I could deal with in a future column.

          • Nancy - January 16, 2012

            Occasionally I do think of a question, but by the time it comes to actually ask it, I’ve forgotten what it was! Middle-Age Memory strikes again!

  • Reply Cheryl - January 18, 2012

    There is another “which” use that often puzzles students — when “which” refers back to a whole idea in a sentence, like: “He got married again a year later, which surprised everyone.” In this case , you can’t say “that”.

    But, it is possible to make two sentences, for emphasis, and use “that” -“He got married again a year later. THAT surprised everyone.”

    • Reply Brett - January 18, 2012

      Great point, Cheryl! The use you mention is covered under supplemental relatives, but it’s certainly worth mentioning on its own. Just to avoid confusion, I’ll point out that the that in Cheryl’s example That surprised everyone is not the subordinator that, but rather the same one in that (man) is my brother. (It’s a determinative, like each, many, some, all, no, etc.)

  • Reply Patricia - January 31, 2012

    Could you write something on capitalization of proper nouns that have recently come into the English language (e.g. web and internet). Should they be capitalized? For example, “I read an article on the web/on the Web?” and “Did you know the Internet/internet is big?”

    • Reply Brett - February 1, 2012

      Hi, Patricia! I don’t think I’d get a whole column out of it, but most dictionaries list Internet with a capital i, and most published sources follow that style; that is most people capitalize it. You can see in the graph I’ve linked to, however, that the capitalized form is becoming less common and the lower-case form is increasing in frequency. Personally, I find the idea that it should be capitalized contrived, and I prefer the uncapitalized version. Would you capitalize the Phone System?

      • Reply Nancy - February 1, 2012

        I think that’s a great question, Patricia. It’s another example of how English is always changing, something my students are always commenting on. Another relatively new phenomenon is the addition of a few new verbs, namely “to text” and “to friend”, which only came into being thanks to social media (which also gave us carpal tunnel syndrome, but that’s another story).

  • Reply ClaudieG - February 3, 2012

    Gotta LOVE that Grammarology….!

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