Commas with “That” and “Which”

Neha Karve

Summary

No comma is needed before or after the word that, whether used as a relative pronoun or a conjunction.

Examples
  • Incorrect: The parcel, that came this morning contained seeds.
    Correct: The parcel that came this morning contained seeds.
  • Incorrect: Today I learned that, islands are mountains in the sea.
    Correct: Today I learned that islands are mountains in the sea.

Use a comma before which when it introduces a nonrestrictive clause (one that provides extra, optional information). Remember to use a comma both before and after the which clause.

Example
  • Incorrect: This shirt which I ordered online is the wrong size.
    Correct: This shirt, which I ordered online, is the wrong size.

Which can replace that to introduce a restrictive clause, providing information essential to meaning. Commas are then omitted. (Such use is seen more often in British than American usage.)

Example
  • Incorrect: Oceanic islands are islands, which do not sit on continental shelves.
    Correct: Oceanic islands are islands which do not sit on continental shelves.

Finally, no comma is needed before or after which when it is used after a preposition or in an indirect question.

Examples
  • This is a story in which nothing happens.
  • They asked which flight we had booked.

That and which

The words that and which are relative pronouns that help describe nouns. Commas are used depending on whether the description is essential to meaning or whether it merely provides additional, optional information.

Examples
  • Cats that like cheese love pizza.
  • I have a shirt that might fit you.
  • Such medicines, which relieve acidity, are called antacids.
  • Anita got a job in Paris, which is what she wanted.

That and which also have other uses. That can be used as a conjunction to introduce a subordinate clause. Which appears in prepositional phrases (in which, on which) and indirect questions.

Examples
  • Anita said that she wanted to go to Paris.
  • The house in which she lived was built in 1913.
  • Ask Tumkin which pizza he wants.

In this article, we discuss when to use commas with that and which.

Comma with that

No comma is needed before or after the word that. As a relative pronoun, that introduces a restrictive clause, which contains a description necessary to identify the person or thing being referred to. Since such information is essential to meaning, it is not enclosed in commas.

Examples
  • Incorrect: Cars, that run on solar power, are better for the environment.
    “Cars are better for the environment” doesn’t convey complete meaning. Which cars? The ones that run on solar power. That introduces a clause essential to meaning; don’t enclose it in commas.
    Correct: Cars that run on solar power are better for the environment.
  • Incorrect: Here is a list of fruits that, last forever in the fridge.
    Correct: Here is a list of fruits that last forever in the fridge.
  • Incorrect: Elephants are mammals, that can’t jump.
    Correct: Elephants are mammals that can’t jump.
  • Incorrect: Your website should have a URL, that’s memorable.
    Correct: Your website should have a URL that’s memorable.
Tip

Don’t use commas around any description essential to meaning (whether or not you use the word that).

Example
  • Incorrect: The phone, I bought online is broken.
    Which phone? The one I bought online.
    Correct: The phone I bought online is broken.

The word that is also used as a conjunction to introduce a subordinate clause. Again, no comma is needed before or after that.

Examples
  • Farley thought that dragonflies were baby dragons.
  • Lulu said that she wanted more cake.
  • I’m glad that you called.

A comma may be used after that if it is followed by an interrupter or other parenthetical phrase.

Examples
  • Anita said that, all things considered, she prefers tea to coffee.
  • We wanted a car that, in the long run, would do less harm to the environment.
  • It was a parcel that, surprisingly, contained seeds.

Comma with which

Use a comma before which when it introduces a nonrestrictive clause (an additional, optional description) in a sentence. Such information may be interesting and even useful but is not essential to meaning. It is therefore enclosed in commas.

Examples
  • Incorrect: Farley’s new phone which he bought just yesterday has already stopped working.
    Even without the which clause, we know which phone is being referred to: Farley’s new phone. Enclose the extra information in commas.
    Correct: Farley’s new phone, which he bought just yesterday, has already stopped working.
  • Incorrect: She comes from Pouthena which is the capital of Nusquam.
    Correct: She comes from Pouthena, which is the capital of Nusquam.
  • Incorrect: This recipe calls for seven eggs which makes no sense at all.
    Correct: This recipe calls for seven eggs, which makes no sense at all.
Caution

Remember to use a comma not just before but also after the which clause.

Example
  • Incorrect: This phone, which I bought ten years ago still works fine.
    Correct: This phone, which I bought ten years ago, still works fine.

The relative pronoun which can also replace that to introduce defining or restrictive clauses (which provide information essential to meaning). Commas are then omitted.

Examples
Note

In formal British usage, which is preferred over that in restrictive clauses (information essential to identify the person or thing being referred to). In contrast, in edited American prose, that is preferred over which.

Example
  • Formal (British): Penguins are birds which cannot fly.
    Formal (American): Penguins are birds that cannot fly.

Don’t use a comma before which when it acts as the complement of a preposition (in which, of which).

Examples
  • Incorrect: The parcel in, which the seeds arrived had no label.
    Correct: The parcel in which the seeds arrived had no label.
  • Incorrect: The book on, which this movie is based was written by a friend of mine.
    Correct: The book on which this movie is based was written by a friend of mine.

Also don’t use a comma before which in indirect and reported questions.

Examples
  • Incorrect: Lulu asked me, which book I wanted.
    Correct: Lulu asked me which book I wanted.
  • Incorrect: I wonder if you know, which bus I should take.
    Correct: I wonder if you know which bus I should take.

Examples from literature

The following examples show how that is used to introduce an essential clause. No commas are necessary or used.

Examples
  • I’ve never come across a definition that satisfied me, though there are some very good ones.
    Virginia Woolf, Night and Day (1919)
  • I was young and not gloomy and there were always strange and comic things that happened in the worst time.
    Ernest Hemingway, A Moveable Feast (1964)

In these sentences, that is used as a conjunction to introduce a subordinate clause. Again, no commas are needed.

Examples
  • And I knew that it was better to live out one’s absurdity than to die for that of others.
    Ralph Ellison, Invisible Man (1952)
  • In university they don’t tell you that the greater part of the law is learning to tolerate fools.
    Doris Lessing, Martha Quest (1952)

Note how a comma is used before which when it introduces an optional, nonessential description.

Example
  • 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)

Finally, when which is used in place of that to introduce a restrictive clause (one that provides information essential to meaning), no commas are used.

Example
  • But there was happiness elsewhere which no description can reach.
    Jane Austen, Mansfield Park (1814)

Usage guide

Don’t use a comma before or after the word that, either as a relative pronoun (when it introduces information essential to meaning) or as a conjunction (when it introduces a relative clause). The word which is also used as a relative pronoun, but it generally presents an optional description, which you should enclose in commas (remember to use commas both before and after the which clause). In British usage, which often replaces that to present information needed to identify the person or thing being referred to; commas are then omitted. When which is used with a preposition (of which, in which), no comma is needed before or after the word. Finally, don’t use a comma with which when it appears in an indirect or reported question.

Examples
  • Correct: That as relative pronoun: Tree kangaroos are marsupials that live in trees.
  • Correct: That as conjunction: You thought that tree kangaroos weren’t real.
  • Correct: Which as relative pronoun (nonrestrictive): Tree kangaroos, which look like a cross between a kangaroo and a lemur, are found in Australia, Indonesia, and Papua New Guinea.
  • Correct: Which as relative pronoun (restrictive): They are marsupials which have evolved to live in trees.
  • Correct: Which as complement of preposition: Here is a list of countries in which tree kangaroos are found.
  • Correct: Which in indirect question: She wanted to know which animal I was talking about.

Quick Quiz

Which is punctuated correctly?
Choose from these answers
All done!
Which is punctuated correctly?
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All done!
Which is punctuated correctly?
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All done!
Which is punctuated correctly?
Choose from these answers
All done!