Defining and non-defining relative clauses
Defining relative clauses
Some relative clause answer questions such as Which one? Where? or Why? For example:
The man who is wearing a grey hat is my brother.
We call these relative clauses, which define or answer a question defining relative clauses. Defining relative clauses are not separated from the rest of the sentence with commas and for people and things, that can replace who or which:
The man that is wearing a grey hat is my brother.
That and which can also be used for things in defining relative clauses.
Ziathora is the name of the book which/that my brother wrote.
As which/that my brother wrote answers the question Which book?, this is a defining relative clause and both which and that can be used.
Non-defining relative clauses
Some relative clauses only give us extra information about the noun they refer to:
Australia, which is a large, dry country, is the only landmass which is a nation, an island and a continent.
The relative clause which is a large, dry country provides extra information and can be left out:
Australia is the only landmass which is a nation, an island and a continent.
We call this kind of relative clause an ‘extra information clause’ or non-defining relative clauses because they do not answer a question such as Which one? Where? or Why? That cannot replace which here.
Let’s look at another example:
My brother Gregory, who was born a few years after me, is an IT specialist.
The relative clause can be left out and that cannot replace who.
Non-defining relative clauses:
- have commas before and after them*
- can be left out as they only contain extra information
- That cannot replace which/who
* The commas in a non-defining relative clause are pauses in spoken language.