Use that, which, and such as correctly#
A restrictive clause is essential to the meaning of a sentence because it limits the noun to which it refers. If you omit a restrictive clause, you change the meaning of the sentence. You can indicate a restrictive clause with the relative pronoun that or who, and you don't set off a restrictive clause with commas.
A nonrestrictive clause doesn't change the core meaning of the sentence. You set off a nonrestrictive clause with commas and can use the relative pronoun which or who in some cases.
| Restrictive clause | Nonrestrictive clause |
|---|---|
| He hired the man who came from Kansas. (Not the man from Idaho) | Jackhammers, which are useful for breaking up concrete, are on sale. |
| Enter the username and password that you just created. (Not the username and password that you created last month) | The hourly backups are rolled into a nightly backup, which is retained for two days. |
| Foods such as pizza and ice cream aren’t very good for you. | Don't hyphenate words that begin with the prefix multi, such as multitenant and multifaceted, unless the root word starts with an i or a capital letter. |
Be sure to clarify restrictive clauses, as follows:
Include the relative pronoun (usually that). You can identify restrictive clauses in which that is missing by looking for two successive nouns.
Don't substitute which for that.
For the use of such as, use a comma before a nonrestrictive clause and don't use a comma for a restrictive clause. You can tell if the clause is nonrestrictive by taking the phrase starting with such as out of the sentence and see whether the sentence is still true. For example:
In this forest, you'll see many types of coniferous trees, such as pine and spruce.
In this forest, you'll see many types of coniferous trees.
See such as in the Alphabetical list of terms for more examples.
| Use | Avoid |
|---|---|
| Enter the username and password that you just created. | Enter the username and password you just created. Enter the username and password which you just created. |
| A task presents information that a user needs to achieve a specific goal. | A task presents information a user needs to achieve a specific goal. A task presents information which a user needs to achieve a specific goal. |