That vs. Which

Summary

Use that to introduce a defining or restrictive clause, which provides information essential to the meaning of a sentence. Don’t enclose this clause in commas.

Example
  • The house that Farley built has fallen down.
    Which house? The one that Farley built. Don’t use commas around a clause necessary to meaning.

Use which instead of that to introduce a non-defining or nonrestrictive clause, which provides additional, optional information. Enclose such a clause in commas.

Example
  • Farley’s house, which he built last year, has fallen down.
    We already know which house: Farley’s house. The which clause provides optional, perhaps interesting information, but it is not necessary to identify what is being described. Enclose it in commas.

Also use which not that to refer to an entire clause or sentence.

Example
  • The ticket doesn’t show what time the ferry leaves, that/which I think is a bit confusing.

While that introduces only restrictive clauses essential to meaning, which can be used to introduce both restrictive and nonrestrictive clauses, particularly in British usage.

Examples
  • Restrictive: The house that/which Farley built has fallen down.
  • Nonrestrictive: Farley’s house, that/which he built last year, has fallen down.

That and which

That and which are relative pronouns. They link relative clauses to nouns. (A relative clause describes a noun or noun phrase.)

Examples
  • The reports that were published last month are now available for download.
    The pronoun that introduces a relative clause that describes the noun phrase “the reports.”
  • Is this the book that won the prize?
  • Penguins are birds that can swim.
  • This book, which is about the refugee experience, has won an award.
  • Farley’s plants, which I was supposed to water, have all died.
  • Poco sent me flowers, which is interesting because he knows I’m allergic to pollen.

There are other ways in which that and which are used. For example, which can be used to ask questions (which book?), and that as an adjective (that book). In this article, we discuss how the words that and which are used as relative pronouns: whether they are used to present essential or nonessential information, with or without commas.

Use of commas: Defining and non-defining

Use that to introduce a defining clause, which helps define or identify the noun being described. Such a clause is essential to the meaning of the sentence and is therefore not enclosed in commas.

Example
  • Defining: The truck that Farley bought yesterday has broken down.
    The clause “that Farley bought yesterday” provides information that is essential to convey complete meaning. There are many trucks in the world. To understand which one is being referred to, we need to know that it is the one that Farley bought yesterday. Since this information is necessary, it is not enclosed in commas.

Which is used instead of that in non-defining clauses, which provide additional, optional information. Since such a clause is parenthetical to the meaning of the sentence, it is enclosed in commas.

Example
  • Non-defining: Farley’s new truck, which he bought just yesterday, has broken down.
    The clause “which he bought just yesterday” provides us with additional information and is enclosed in commas. We already know which truck broke down: Farley’s new truck. The which clause gives additional details that may be useful or interesting but are not necessary to understand what is being talked about.

Restrictive vs. nonrestrictive

Defining clauses are restrictive: they limit or restrict the meaning of the noun being described. A clause introduced by that is always restrictive. No commas are used around such a clause.

Example
  • Restrictive (defining): The report that was released yesterday is available for download.
    There may be many reports. Which report are we referring to? The one that was released yesterday. The that clause helps identify the report—it restricts the identity of the report to the description given.

Non-defining clauses are nonrestrictive: they don’t limit the meaning to the description given. Instead, they provide additional details. Use which instead of that to introduce a nonrestrictive clause. Since such a clause provides additional, parenthetical information, it is enclosed in commas.

Example
  • Nonrestrictive (non-defining): The latest report, which was released this morning, is now available for download.
    Which report? We already know which one: the latest one. The clause “which was released this morning” provides additional details not necessary to identify the report.

When to use that

Use that to introduce a clause that presents information essential to the meaning of a sentence. Since this information is necessary to identify the person or thing being referred to, don’t enclose it in commas.

Examples
  • Incorrect: The parcel, that arrived yesterday, has gone missing.
    We don’t know which parcel is being referred to until we are told it is the one that arrived yesterday. Since this information is necessary rather than parenthetical, it shouldn’t be enclosed in commas.
    Correct:The parcel that arrived yesterday has gone missing.
  • Incorrect: You can have shoes, that are either pretty or comfortable, not both.
    Correct:You can have shoes that are either pretty or comfortable, not both.
  • Incorrect: Here is a copy of the report, that was published this morning.
    Correct: Here is a copy of the report that was published this morning.

That introduces a defining clause, which means it helps identify the person or thing being described. A that clause is thus restrictive: it narrows down the reference to the description given.

Examples
  • The bottle that we found on the shore contained a city of little people.
    Which bottle? The one that we found on the shore.
  • These are the people that I told you about.
  • The stone that Tumkin found was a diamond.
Caution

Don’t use a comma before a clause introduced by that.

Example
  • Incorrect: Maya needs sandals, that don’t hurt her ankles.
    The clause that don’t hurt her ankles is essential to the sentence. It tells us which sandals Maya needs. It is not optional or parenthetical information. Don’t enclose it in commas.
    Correct: Maya needs sandals that don’t hurt her ankles.

Omitted that

In a relative clause, if that is not the subject, it may be omitted without loss of meaning.

Example
  • The tickets (that) we booked yesterday have already been canceled.
    The subject of the relative clause “that we booked yesterday” is we (the word before the verb booked). The pronoun that can safely be omitted without loss of meaning.
    Correct: The tickets we booked yesterday have already been canceled.

Such omission is not possible when that is the subject of the relative clause.

Example
  • The ticket that got booked is in your name.
    The subject of the relative clause “that got booked” is that (the word before the verb got booked). It cannot be omitted.
    Incorrect: The ticked got booked is in your name.
Tip

It is sometimes thought that that can refer only to things and not to people. This understanding is incorrect. That can be used not just for things but also for people.

Examples
  • Correct: The woman who/that called this morning is now at the door.
  • Correct: The people whom/that you meet are always strangers.

In contrast, which doesn’t usually refer to people.

When to use which

When you use which to introduce additional information not necessary to meaning, enclose the clause in commas.

Examples
  • My trusty old car, which I bought fourteen years ago, has finally broken down.
  • We must protect the ice caps, which are melting at an alarming rate.
  • The eggs need to be cooked, which can be done any way you like.

When used with commas, which introduces a nonrestrictive clause: it does not limit meaning and is not necessary to identify the thing being talked about. We already know what is being referred to. The which clause just gives us additional, interesting details.

Examples
  • It all began at midnight, which is when everything happens.
    The clause “which is when everything happens” is simply giving more information. The main clause “It all began at midnight” is complete in meaning even without the which clause.
  • They went to Patagonia, which is heaven on earth.
Caution

Don’t forget to “close” your commas. A comma should appear both before and after your which clause.

Example
  • Incorrect:The dodo, which was a flightless bird endemic to Mauritius went extinct in the 1600s.
    Correct: The dodo, which was a flightless bird endemic to Mauritius, went extinct in the 1600s.

Which can also be used restrictively (in place of that) to present essential information. Commas are then omitted. Such use is more common in British than in American usage.

Examples
  • Here is a diamond which/that we found on the beach.
    The which clause is now essential (like a that clause). Which diamond? The one which we found on the beach. Don’t enclose it in commas. Note that you can use either that or which, that being preferred in American formal writing.
  • Is that the letter which/that came today?
  • I have a key which/that can open any door.
Tip

If removing the clause makes the sentence lose meaning, don’t use commas. If overall meaning is unaffected by removing the clause, enclose it in commas.

Examples
  • The book which you wanted isn’t available.
    The clause “which you wanted” is essential to meaning (it tells us which book is being referred to). Don’t use commas.
  • Maya has written a new book, which just happens to be about dinosaurs.
    The clause “which just happens to be about dinosaurs” provides additional, parenthetical information. Enclose it in commas.

Which is also used restrictively (without commas) when using that would be inelegant—for example, two consecutive thats or a series of thats.

Example
  • Poor: Fight for that that is right.
    Better: Fight for that which is right.

Reference to a whole clause or sentence

Use which not that to refer to an entire clause or sentence. Which is frequently used in this way to present an opinion or evaluation.

Examples
  • I had hoped to climb Mt. Everest, that/which doesn’t seem possible anymore.
    The pronoun which refers not just to “Mt. Everest” but to the entire clause “I had hoped to climb Mt. Everest.” Compare this to “Rita climbed Mt. Everest, which is the tallest mountain in the world.”
  • Maya loves cheese, that/which is why she now lives in Switzerland.
  • Insert an em dash, that/which you can do in three ways.

American vs. British usage

In British style, which and that are used interchangeably in restrictive or defining clauses (i.e., in clauses essential to meaning). Such clauses are not enclosed in commas.

Examples
  • British: The boat which/that Farley built has sunk to the bottom of the lake.
  • British: This was something which/that had to happen.
  • British: Stories which/that speak to the human condition are the ones that survive.

In contrast, in American usage, that instead of which is generally used in restrictive or defining clauses (those essential to meaning), especially in formal (such as academic) writing.

Examples
  • American: The boat that Farley built has sunk to the bottom of the lake.
  • American: This was something that had to happen.
  • American: Stories that speak to the human condition are the ones that survive.
Note

American style manuals like the AP Stylebook and APA Publication Manual recommend using that to present essential information (without commas) and which for optional information (with commas), which is perhaps why this distinction is maintained in U.S. academic and formal writing. The Chicago Manual of Style notes that the distinction is generally seen in edited prose, though it admits that British editors and writers freely use which in place of that.

Even in American usage, this “rule” about using that to present essential information and which for optional details is not as strictly followed as some would believe. The following examples illustrate how American writers do use which restrictively.

Examples
  • I was trying to write then . . . what the actual things were which produced the emotion that you experienced . . . the sequence of motion and fact which made the emotion and which would be as valid in a year or in ten years or, with luck and if you stated it purely enough, always.
    Ernest Hemingway, Death in the Afternoon (1932)
  • There is no crime which a boy of eleven had not envisaged long ago.
    William Faulkner, The Reivers (1962)

Examples from literature

Here are some examples from writing that show how that is used without commas to introduce a restrictive clause.

Examples
  • Existence seems to me now the most remarkable thing that could ever be imagined.
    Marilynne Robinson, Gilead (2004)
  • One sad thing about this world is that the acts that take the most out of you are usually the ones that people will never know about.
    Anne Tyler, Celestial Navigation (1974)
  • Perhaps it was a knack that humans had, for cleaning up their untidy existences—a hidden survival weapon, like antibodies in the bloodstream.
    Rohinton Mistry, A Fine Balance (1995)
  • An infectious and deadly coronavirus that has killed thousands in China has spread to at least 46 countries, stirring fears that COVID-19 may soon become a pandemic.
    — “Fears of pandemic stoked as more countries confirm COVID-19 cases,” UPI (Feb. 27, 2020)

The following examples from writing show which used with commas (i.e., to introduce a non-defining or nonrestrictive clause) to provide additional information.

Examples
  • Pink is supposed to weaken your enemies, make them go soft on you, which must be why it’s used for baby girls.
    Margaret Atwood, Cat’s Eye (1988)
  • For the faithful, the patient, the hermetically pure, all the important things in this world—not life and death, perhaps, which are merely words, but the important things—work out rather beautifully.
    J.D. Salinger, Seymour: An Introduction (1959)
  • Florida, which averaged more than 20,000 cases a day during much of August, is now reporting around 2,200 new infections daily.
    — “Coronavirus in the U.S.: Latest Map and Case Count,” New York Times (Oct. 22, 2021)

And here are a couple of examples of which used without commas, or restrictively, to present essential information.

Examples
  • Often the mass emotions are those which seem the noblest, best and most beautiful.
    Doris Lessing, Prisoners We Choose to Live Inside (1986)
  • So you’ve got a business idea which you’re sure is going to make you money – but just how do you get the ball rolling?
    — “DIY Generation: How to Be Your Own Boss by 25,” BBC News (Oct. 31, 2018)

Quick Quiz

Which is punctuated correctly?
Choose from these answers
All done!
Which is correct?
Choose from these answers
All done!
Which of these is preferred in American usage?
Choose from these answers
All done!
Which is/are acceptable in British usage?
Choose from these answers
All done!
Which is punctuated correctly?
Choose from these answers
All done!

Did You Know?

Any may be either singular or plural (Is/are any of you going to help me?).
Know more:Any Is or Are: Is Any Singular or Plural?