Look at the example sentences. Do you notice any differences between a and b?
A defining relative clause adds necessary information to the main clause. Without it, the main clause would be incomplete. There are no commas.
A non-defining relative clause adds extra (zusätzlich) information to the main clause. It is not necessary and the main clause is complete without it. There are commas between the main clause and the relative clause.
There’s a special type of relative clause that is used very often especially in spoken English. Compare the following sentences:
In the a-example sentences, the relative clause has its own subject. In this case, the relative pronoun (who, which, that) can be omitted [weglassen].
So the a-examples could also read:
Here are some more examples
This type of defining relative clause is called a contact clause.
object1) | subject2) | ||||
contact clause | The castle | (which) | you | can visit | is on the hill |
---|---|---|---|---|---|
normal relative clause | The castle | which | stands | on the hill is nice. | |
contact clause | The city | (that) | I | love | is Edinburgh. |
normal relative clause | The city | that | is | 500 years old has many houses. | |
contact clause | The power station | (which) | I | am working on | will be finished soon. |
normal relative clause | The power station | which | works | with water is very new. |
If the relative clause has its own subject, we can leave out the relative pronoun (who, which, that).
You can also say this in a different way:
When the relative pronoun is the object of the relative clause, you can leave it out.)