Relative clauses are used to give us more information about people or things:
There are two types of relative clause:
- Defining clause. This is necessary information that is needed to understand meaning
This is the book that I bought from the second hand book shop on the high street.
- Non-defining clause. This is to add unnecessary information.
This is the house, where I called you from yesterday, where I will celebrate my birthday.
Pronouns and their differences:
Who/that (people) – I can see a man who is jogging in the park.
Whom (preposition + person) – This is my friend with whom I usually work out [formal]
Whose (possession) – These are my students whose coursework is exceptional.
Where (place) – This is the bar where I normally have breakfast
When (time/date) – That was the day when we celebrated our wedding.
Which/that (thing) – These are the books which were ordered by mistake.
DO NOT USE THAT WITH (COMMAS) – This is the pen, that was expensive, we bought from Harrods.
USE WHICH INSTEAD – This is the pen, which was expensive, we bought from Harrods.