As the name suggests, defining relative clauses give essential information to define or identify the person or thing we are talking about. Take for example the sentence: Dogs that like cats are very unusual. In this sentence we understand that there are many dogs in the world, but we are only talking about the ones that like cats. The defining relative clause gives us that information. If the defining relative clause were removed from the sentence, the sentence would still be gramatically correct, but its meaning would have changed significantly.
Defining relative clauses are composed of a relative pronoun (sometimes omitted), a verb, and optional other elements such as the subject or object of the verb. Commas are not used to separate defining relative clauses from the rest of the sentence. Commas or parentheses are used to separate non-defining relative clauses from the rest of the sentence.
- Children who hate chocolate are uncommon.
- They live in a house whose roof is full of holes.
- An elephant is an animal that lives in hot countries.
- Let's go to a country where the sun always shines.
- The reason why I came here today is not important.
The following relative pronouns are used in defining relative clauses. These relative pronouns appear at the start of the defining relative clause and refer to a noun that appears earlier in the sentence.
Replacing with "that" in spoken English
The pronouns who, whom, and which are often replaced by that in spoken English. Whom is very formal and is only used in written English. You can use who or that instead, or omit the pronoun completely. In the examples below, the common usage is given with the defining relative clause highlighted. The pronoun that would be used in more formal written English instead of that is given in parentheses.
- The dish that I ordered was delicious. (which)
- The man that came with her has already left. (who)
- The doctor that I was hoping to see wasn't on duty. (whom)
Including or omitting the relative pronoun
The relative pronoun can only be omitted when it is the object of the clause. When the relative pronoun is the subject of the clause, it cannot be omitted. You can usually tell when a relative pronoun is the object of the clause because it is followed by another subject + verb. See below, in the first sentence the relative pronoun cannot be ommitted because it is the subject of the relative clause ("the woman spoke"). In the second sentence, the pronoun can be omitted because "the woman" is the object of the verb "loved".
|Noun, subject of the main clause||Relative pronoun||Verb + rest of relative clause||Verb + rest of main clause|
|The woman||that||spoke at the meeting||was very knowledgeable.|
|The woman||(that)||the man loved||was living in New York.|
Other uses of "that"
'That' is often used to introduce defining relative clauses when they follow the words something, anything, everything, nothing, all or a superlative. It may be omitted when it is not the subject of the clause.
- There's something (that) you should know.
- It was the best film (that) I've ever seen.
- Do you have anything that will help my throat?
- Everything (that) you say seems silly to me.
- Nothing (that) anyone does can replace my lost bag.
- I'm sorry, but that is all (that) I saw.