Do you know the difference between everyday US and UK terminology? Test yourself with this quiz on words that differ across the Atlantic.
Question 1 of 7
In the UK, COTTON CANDY is more commonly known as…

Idioms about that

Origin of that

First recorded before 900; Middle English; Old English thæt (pronoun, adjective, adverb, and conjunction), originally, neuter of se “the”; cognate with Dutch dat, German das(s), Old Norse that, Greek tó, Sanskrit tad

grammar notes for that

4. When that introduces a relative clause, the clause is usually restrictive; that is, essential to the complete meaning of the sentence because it restricts or specifies the noun or pronoun it modifies. In the sentence The keys that I lost last month have been found, it is clear that keys referred to are a particular set. Without the that clause, the sentence The keys have been found would be vague and probably puzzling. That is used to refer to animate and inanimate nouns and thus can substitute in most uses for who ( m ) and which: Many of the workers that (or who ) built the pyramids died while working. The negotiator made an offer that (or which ) was very attractive to the union. Experienced writers choose among these forms not only on the basis of grammar and the kind of noun referred to but also on the basis of sound of the sentence and their own personal preference.
The relative pronoun that is sometimes omitted. Its omission as a subject is usually considered nonstandard, but the construction is heard occasionally even from educated speakers: A fellow ( that ) lives near here takes people rafting. Most often it is as an object that the relative pronoun is omitted. The omission almost always occurs when the dependent clause begins with a personal pronoun or a proper name: The mechanic ( that ) we take our car to is very competent. The films ( that ) Chaplin made have become classics. The omission of the relative pronoun as in the two preceding examples is standard in all varieties of speech and writing.
13. The conjunction that, which introduces a noun clause, is, like the relative pronoun that, sometimes omitted, often after verbs of thinking, saying, believing, etc.: She said ( that ) they would come in separate cars. He dismissed the idea ( that ) he was being followed. As with the omission of the relative pronoun, the omission of the conjunction almost always occurs when the dependent clause begins with a personal pronoun or with a proper name. This omission of the conjunction that occurs most frequently in informal speech and writing, but it is a stylistic option often chosen in more formal speech and writing.


that , which (see grammar note at the current entry)
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2023


What’s the difference between that and which?

That and which are used in very similar ways (especially to introduce clauses that refer back to an earlier part), but there is often a key difference.

Before we get into the grammar, let’s take a look at two similar sentences, one using that and one using which.

I wrote about my favorite movie that was released in 1994. 

I wrote about my favorite movie, which was released in 1994. 

Both sentences are about a movie. But there’s a difference in what’s being communicated.

In the first sentence (the one using that), the speaker is indicating that the movie they wrote about is their favorite movie released in 1994—not necessarily their favorite movie in general.

In the second sentence (the one using which), the speaker is saying that the movie is their favorite in general, while also mentioning that it was released in 1994. In this sentence, you could take away the part that starts with which and the sentence would retain the same basic meaning.

But that’s not true of the first sentence—taking away that was released in 1994 would alter the meaning of the sentence.

That’s because that was released in 1994 is what’s called a restrictive clause, which is a part of a sentence that provides essential information about the part before it. A restrictive clause can’t be removed without changing the essential meaning of the sentence.

The second sentence (the one using which), ends in a nonrestrictive clause, which provides nonessential information—information that can be removed without altering the main message of the sentence. Usually, nonrestrictive clauses are marked off by commas (or em dashes). Think of a nonrestrictive clause as an aside—additional information mentioned along the way.

This grammatical distinction between that and which is largely used in formal American English. In informal speech, it is very common to use that and which interchangeably. And sometimes the difference in what they convey is very subtle or practically nonexistent.

Still, when used in clauses like the ones in our examples, which is usually preceded by a comma, but that is not.

Want to learn more? Read the full breakdown of the difference between that and which.

Quiz yourself on that vs. which!

Should that or which be used in the following sentence?

The cat ____ I saw yesterday has come back.

How to use that in a sentence

British Dictionary definitions for that

Word Origin for that

Old English thæt; related to Old Frisian thet, Old Norse, Old Saxon that, Old High German daz, Greek to, Latin istud, Sanskrit tad

usage for that

Precise stylists maintain a distinction between that and which : that is used as a relative pronoun in restrictive clauses and which in nonrestrictive clauses. In the book that is on the table is mine, the clause that is on the table is used to distinguish one particular book (the one on the table) from another or others (which may be anywhere, but not on the table). In the book, which is on the table, is mine, the which clause is merely descriptive or incidental. The more formal the level of language, the more important it is to preserve the distinction between the two relative pronouns; but in informal or colloquial usage, the words are often used interchangeably
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Other Idioms and Phrases with that


The American Heritage® Idioms Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.