The relative pronoun that can refer to both people and things. In other words, it can replace both who and which. However, this is not always possible. That cannot be used in non-identifying relative clauses. Note that a non-identifying relative clause can be easily removed from the sentence. An identifying relative clause, on the other hand, cannot be removed that easily. If it is removed from the sentence, the meaning will change.
- They opposed the motion that / which was proposed by the rival group.
Now remove the relative clause ‘that / which was proposed by the rival group’ and you will get the simple sentence ‘They opposed the motion’.
As you can see, this sentence does not mean the same as the original sentence because it doesn’t identify the motion under discussion.
Now consider another sentence.
- My sister, who lives in New York, is a classical dancer. (NOT My sister, that lives in New York,…)
Here the relative clause who lives in New York is non-identifying. It merely provides additional information. Even if you remove it from the sentence the meaning doesn’t change.
- My sister is a classical dancer.
As you can see, this sentence means the same as the original sentence; it just doesn’t give as much information.
In writing, non-identifying relative clauses are separated by commas.
Exercise
State whether the relative clauses in the following sentences are identifying or non-identifying and rewrite them using appropriate punctuation marks.
1. I have got a book which is really interesting to read.
2. I met a girl who sells flowers.
3. Maya who sells flowers in the street is a pretty girl.
4. This is Jane who works with my sister.
Answers
1. Identifying (No commas are required.)
2. Identifying (No commas are required)
3. Non-identifying (Maya, who sells flowers in the street, is a pretty girl.)
3. Non-identifying (This is Jane, who works with my sister.)