• EM |
• Articles |
• Usage |
• Pronouns

That vs. Which

Neha Karve

Updated April 12, 2022

Summary

Use that to introduce information essential to meaning (a defining or restrictive clause). Don’t use a comma before that.

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 additional, optional information (a non-defining or nonrestrictive clause). Enclose such information 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 instead of that to refer to an entire clause.

Example

• The ticket doesn’t show what time the ferry leaves, that/which is confusing.
  Which refers to the entire clause that precedes it.

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.)

There are other ways in which that and which are used. For example, which can be used to ask questions (which book?), and that can act 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.

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.

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.

Omitted that

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

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

When to use which

Use which instead of that to present additional information not necessary to meaning. Since this information is optional (or parenthetical), it is enclosed in commas.

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.

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.

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

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.

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.

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.

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.

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.

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.

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.

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 from literature

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

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

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