Relative clauses give us information about the subject or object of a main clause.
Defining relative clause describes exactly which person or thing we mean.
- Arthur Conan Doyle is the writer who invented Sherlock Holmes.
- Do you have a phone which takes photos?
Non-defining relative clause does not describe exactly who or what we mean.
- Alexander Solzhenitsyn, who was awarded the Nobel Prize in 1970, wrote several novels.
If we remove the sentence, it still makes sense:
- Alexander Solzhenitsyn wrote several novels.
The difference in meaning
Because non-defining relative clauses do not identify the subject in the main clause, there
is a difference in meaning:
DEFINING
- The passengers who were injured in the crash were taken to hospital. (Only the injured passengers were taken to hospital. We know that some were not injured.)
NON-DEFINING
- The passengers, who were injured in the crash, were taken to hospital. (All the passengers were taken to hospital. We know that they were all injured.)
Spelling
Unlike defining relative clauses, non-defining relative clauses are separated from the rest of
the sentence by commas. We usually put the clause immediately after the subject it refers to:
✘ The author of the-novel lives in Edinburgh, which- you can buy for $20.
✔ The author of the novel,which you can buy for 20, lives in Edinburgh.
That and What
We don't use that or what in non-defining relative clauses:
✘ The painting, that is now restored, can be seen in -the National Gallery.
✔ The painting,which is now restored,can be seen in the National Gallery.
