[ wich, hwich ]
/ wɪtʃ, ʰwɪtʃ /
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Should you take this quiz on “shall” versus “should”? It should prove to be a quick challenge!
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Which form is used to state an obligation or duty someone has?

Origin of which

First recorded before 900; Middle English; Old English hwilc, hwelc, equivalent to hwe-, base of hwā interrogative pronoun, + -līc “body, shape, kind”; cognate with Old Frisian hwelik, Dutch welk, German welch, Gothic hwileiks literally, “of what form”; see origin at who, like1

usage note for which

The relative pronoun which refers to inanimate things and to animals: The house, which we had seen only from a distance, impressed us even more as we approached. The horses which pulled the coach were bay geldings. Formerly, which referred to persons, but this use, while still heard ( a man which I know ), is nonstandard. Contrary to the teachings of some usage guides, which introduces both restrictive and nonrestrictive clauses. The “rule” that which can be used only with nonrestrictive clauses has no basis in fact. In edited prose three-fourths of the clauses in which which is the relative pronoun are restrictive: A novel which he later wrote quickly became a bestseller. See also that.


that, which (see grammar note at that)
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2022


What’s the difference between which and that?

Which and that 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 which and that.

Quiz yourself on which vs. that!

Should which or that be used in the following sentence?

The cat ____ I saw yesterday has come back.

How to use which in a sentence

British Dictionary definitions for which

/ (wɪtʃ) /

  1. used with a noun in requesting that its referent be further specified, identified, or distinguished from the other members of a classwhich house did you want to buy?
  2. (as pronoun)which did you find?
  3. (used in indirect questions)I wondered which apples were cheaper
  1. whatever of a class; whicheverbring which car you want
  2. (as pronoun)choose which of the cars suit you
used in relative clauses with inanimate antecedentsthe house, which is old, is in poor repair
as; and that: used in relative clauses with verb phrases or sentences as their antecedentshe died of cancer, which is what I predicted
the which archaic a longer form of which, often used as a sentence connector

Word Origin for which

Old English hwelc, hwilc; related to Old High German hwelīh (German welch), Old Norse hvelīkr, Gothic hvileiks, Latin quis, quid

undefined which

See that
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 which


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