Grammar use of the word which

There’s a lot of confusion about that and which. These two words are often used interchangeably, even though they’re not necessarily interchangeable.

Historically, that and which may have carried the same meaning, and some English dialects may allow for that and which to be swapped without affecting the meaning of a sentence.

However, in American English, the grammar rules offer a distinct difference between the two words. By the time you’re done reading this post, you’ll fully understand the difference between that and which, and you’ll be able to use both words correctly.

That and Which

As with most grammar rules, there are exceptions and exemptions from the standard ways that and which should be used in a sentence. To gain understanding of confusing word pairs, it’s always best to start with the basics. As we look at how to properly use that and which, we’ll focus on simple, standard usage.

Relative Pronouns

From Wikipedia: “A relative pronoun is a pronoun that marks a relative clause within a larger sentence. It is called a relative pronoun because it relates to the word that it modifies.”

Like adjectives and adverbs, relative pronouns modify other words. Adjectives modify nouns:

• I have a car.
• I have a red car.

Adverbs modify verbs:

• I am walking.
• I am walking quickly.

The main difference between adjectives and adverbs is that adjectives usually modify things (nouns) while adverbs modify actions (verbs). Relative pronouns also modify words, but they often do so as clauses rather than as single, descriptive words. In the examples below, the clauses are italicized.

• Bring me the bucket.
• Bring me the bucket that has apples in it.
• The bucket, which has apples in it, is blue.

The difference between the words that and which and how they are used as relative pronouns depends on whether the clause they belong to is restrictive or nonrestrictive.

Restrictive and Nonrestrictive Clauses

Restrictive Clauses Are Necessary

A restrictive clause is necessary to the meaning of a sentence. For example:

• I want the bucket that has apples in it.

If you removed the clause “that has apples in it,” the meaning of the sentence would be lost. Nobody would know which bucket the speaker wants. The clause is necessary to the meaning of the sentence and is therefore a restrictive clause. Because it’s a restrictive clause, it should take the relative pronoun that.

Nonrestrictive Clauses are Unnecessary

A nonrestrictive clause is not necessary to the meaning of a sentence. In fact, it can be removed from a sentence without affecting its meaning. For example:

• The bucket, which is blue, has apples in it.
• There are apples in the bucket, which is blue.

If you removed the nonrestrictive clause “which is blue,” from either of the sentences above, the meaning of the sentences would not be lost. We’d still know that the bucket has apples in it. Note that in the second example, the nonrestrictive clause adds information about something that has already been identified. Because the clause is unnecessary to the meaning of the sentence, we know it’s a nonrestrictive clause, and therefore should take the relative pronoun which.

• Use that before a restrictive (necessary) clause.
• Use which before a nonrestrictive (unnecessary) clause.

Restrictive and non-restrictive relative clauses

Using ‘which’ in a question

Using ‘which’ in a relative clause

Use ‘which’ or ‘who’

Use of ‘which’ with ‘of’

Use of ‘which’ to avoid repetitions

Sometimes, if you have already used ‘that’ in a sentence, you may choose to write ‘which’ in order to avoid repetition of the word ‘that’. For instance, ‘that which you cannot see’. In this sentence, ‘which’ is used because ‘that’ was already used and you cannot write two ‘that’ words in a sentence. Whether it is required or not, this kind of sentence is often constructed to avoid any awkward formations. ‘That that you cannot see’ is not technically incorrect, but the use of ‘which’ instead of a second ‘that’ is more preferable.

If you want to read similar articles to How To Use The Word ‘Which’ In A Sentence, we recommend you visit our Learning category.

Do you suffer from low self-esteem? Do you have anxiety, or difficulty making decisions? Do you find yourself unable to decide whether you should use that or which when composing a sentence? In the event that you answered “yes” to either of the first two questions you have our sympathies, but as a dictionary we can offer little else. However, if the source of your trouble is the issue of that and which we may be of some small assistance.

Restrictive and Unrestrictive Clauses

Before we begin, you should be warned that it’s time to put your grammar pants on, since we’re about to dive into the world of restrictive and nonrestrictive clauses. (If you don’t know what grammar pants are, they are itchy woolen slacks that are too tight, and magically make you mildly dissatisfied with the choices of everyone around you.)

Once upon a time, long ago, when the English language was still basking in its Edenic youth, that and which were freely interchanged. Everyone was very happy.

Render therefore unto Caesar the things which are Caesars; and unto God the things which are Gods.
—Joseph Hall, A Plaine and Familiar Explication, 1633

Render therefore unto Caesar, the things that are Caesars; and unto God, the things that are Gods.
—Robert Grosse, Royalty and Loyalty, 1647

Render therefore unto Caesar the things that are Caesar’s, and unto God the things which are God’s.
—Samuel Sturmy, The Mariners Magazine, 1669

Render therefore unto Caesar the things which are Caesars: and unto God the things that are Gods.
—Richard Hollingworth, An Exercitation Concerning Usurped Powers, 1650

The careful reader may have noticed that in the four examples given above, all published within a span of four decades, each of the authors writes what is essentially the same sentence, but uses that and which in a manner that is different from each of the others. The mid-17th century was apparently a period of syntactical free love. Then the rules on restrictive and nonrestrictive clauses came along.

If you are not a copy editor, or someone who is deeply interested in grammar, you may have forgotten what restrictive and nonrestrictive clauses are. A restrictive clause is a part of a sentence that may not be removed without rendering that sentence incomplete, difficult to understand, or with its meaning substantially changed. “The essay that covers grammar is very boring” contains a restrictive clause (“that covers grammar”) that is important in making the sentence understood. “The essay that covers grammar, which I read while I was supposed to be working, is very boring,” contains the same restrictive clause, but also has a nonrestrictive clause (“which I read while I was supposed to be working”). This nonrestrictive clause adds information to the sentence, but it is not imperative to include it.

If you would prefer a sartorial analogy, the nonrestrictive clause functions like a silk scarf; you may wish to wear one when leaving the house, but your day won’t really be affected if you decide to leave it at home. The restrictive clause, however, is more akin to pants; your day will have a decidedly problematic tone if you leave home without them.

That underwent a period of decline at the end of the 17th century, then made a comeback several decades later. When it reappeared, that was used for nonrestrictive clauses much less frequently than it had previously been (although some writers, such as Thackeray and Tennyson, still used it in this way quite often).

Rules for ‘Which’ and ‘That’

Soon, grammarians tried to establish a set of rules to govern the use of these words. As is so often the case when a grammatical rule is established based on the preference of usage writers, rather than actual usage, there was a great deal of disagreement as to what the rules should actually be. In 1906 the Fowler brothers (Henry Watson and Francis George) published The King’s English, and came up with a firm set of guidelines which were adopted by many subsequent usage guides (the Fowlers used the terms defining and non-defining instead of restrictive and nonrestrictive).

That should never be used to introduce a non-defining clause.

…Which should not be used in defining clauses except when custom, euphony, or convenience is decidedly against the use of that.

—Fowler, F.G. & H.W., The King’s English, 1906

There are some problems with these rules. The main one is that they don’t really work. Some twenty years after the brothers first issued them, Henry Watson wrote another book on usage. He plaintively expressed his feelings on the way that people were treating that and which:

…if writers would agree to regard that as the defining relative pronoun, & which as the non-defining, there would be much gain both in lucidity & in ease. Some there are who follow this principle now; but it would be idle to pretend that it is the practice either of most or of the best writers.
—H. W. Fowler, A Dictionary of Modern English Usage, 1926

It has been pointed out that if most of your language’s writers do not follow a rule (and the best writers seem to disregard it as well) then you may have to accept that it’s not much of a rule. Another issue with the Fowler’s dicta is that if you say that your rule can be ignored for reasons of “custom, euphony, or convenience”, it would appear to be more of a mild suggestion than a rule.

It is true that that is rarely found today used in nonrestrictive clauses (although poets still use it thusly), but which seems to have a fair degree of flexibility to it, and can perform very nicely in restrictive clauses, nonrestrictive clauses, and in annoying people who feel that it should never be found outside of a nonrestrictive clause. Here is what our own usage guide, the Merriam-Webster Dictionary of English Usage, has to say on the matter:

We conclude that at the end of the 20th century, the usage of which and that—at least in prose—has pretty much settled down. You can use either which or that to introduce a restrictive clause—the grounds for your choice should be stylistic—and which to introduce a nonrestrictive clause.

Another way of looking at this is that if your clause is bracketed by commas (“the article on grammar, which I started while eating lunch, seemed to never end”) it is likely a nonrestrictive clause, and you can give it a which. If it is not surrounded by commas, then it is most likely a restrictive clause, and you can choose to give it a that or a which. If anyone questions your decision, you can say that you are following the advice of the Fowlers, and are making a decision based on custom, euphony, and convenience.