by Liz Walter
There are two main types of relative clause. One is for making it clear who or what we are talking about. Teachers call this type ‘defining relative clauses’, and they don’t have commas around them:
The woman who gave me the flowers is my neighbour.
This is the chair that I bought yesterday.
The other type is for giving extra information. These are called ‘non-defining relative clauses’, and they do have commas:
The woman, who was a friend of mine, gave me some flowers.
The furniture, which was very old, belonged to my father.
For these, we use who for people and which for things. We don’t use ‘that’.
One very common mistake that learners of English make with relative clauses is to put in an extra pronoun when it isn’t needed:
The woman who gave me the flowers she is my neighbour.
Remember, ‘The woman who gave me the flowers’ is the subject of the sentence. You don’t need another subject, so don’t add ‘she’.
In just the same way, if the relative clause is the object, don’t add another object pronoun. Don’t say, for example ‘This is the chair that I bought it yesterday.’ ‘The chair that I bought’ is the object, so don’t add ‘it’.
These are the most important things to know about relative clauses, but the following tips may also be useful. Firstly, the possessive pronoun we use in relative clauses is always whose. It doesn’t matter if we’re talking about a person or a thing:
She is the child whose mother called me.
The house, whose walls were thick, was cool inside.
Secondly, it is common to miss out the pronoun in defining clauses when the pronoun is the object of the clause. So, for example, you can say:
This is the chair I bought yesterday.
However, if it’s the subject, you have to keep the pronoun:
This is the chair that has the broken leg.
And finally, a word about whom. In very formal English, this pronoun is used when a person is the object of the sentence:
She is the woman whom I saw yesterday.
However, in reality, whom is very rarely used, unless it is to avoid ending a sentence with a preposition. For a very formal piece of writing, you might prefer ‘the woman to whom I gave the document’ to ‘the woman (who) I gave the document to’, but frankly, if ending a sentence with a preposition is your worst crime, you’re doing pretty well!