Use that and which 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 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 the relative pronoun which or who.
| 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. |
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.
| 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. |