We use defining relative clauses to give essential information about someone or something – information that we need in order to understand what or who is being referred to. A defining relative clause usually comes immediately after the noun it describes.
We usually use a relative pronoun (e.g. who, that, which, whose and whom) to introduce a defining relative clause (In the examples, the relative clause is in bold , and the person or thing being referred to is underlined.):
They’re the people who want to buy our house .
Here are some cells which have been affected .
They should give the money to somebody who they think needs the treatment most .
[talking about an actress]
Spoken English:She’s now playing a woman whose son was killed in the First World War .
In defining relative clauses we often use that instead of who, whom or which. This is very common in informal speaking:
They’re the people that want to buy our house.
Here are some cells that have been affected.
The relative pronoun can define the subject or the object of the verb:
They’re the people who/that bought our house . (The people bought our house. The people is the subject.)
They’re the people who/that she met at Jon’s party . (She met the people. The people is the object.)
Here are some cells which/that show abnormality . (Some cells show abnormality. Some cells is the subject.)
Here are some cells which/that the researcher has identified . (The researcher has identified some cells. Some cells is the object.)
We often leave out the relative pronoun when it is the object of the verb:
They’re the people she met at Jon’s party .
Here are some cells the researcher has identified .
In writing, we don’t use commas in defining relative clauses:
This is a man who takes his responsibilities seriously.
Not: This is a man, who takes his responsibilities seriously .
When the relative pronoun is the subject of the relative clause, we don’t use another personal pronoun or noun in the relative clause because the subject (underlined) is the same:
She’s the lady who lent me her phone. (who is the subject of the relative clause, so we don’t need the personal pronoun she)
Not: She’s the lady who she lent me her phone .
There are now only two schools in the area that actually teach Latin. (that is the subject of the relative clause, so we don’t need the personal pronoun they)
Not: There are now only two schools in the area that they actually teach Latin .
When the relative pronoun is the object of the relative clause, we don’t use another personal pronoun or noun in the relative clause because the object (underlined) is the same:
We had a lovely meal at the place which Phil recommended . (which is the object of the relative clause, so we don’t need the personal pronoun it)
Not: We had a lovely meal at the place which Phil recommended it .
We use non-defining relative clauses to give extra information about the person or thing. It is not necessary information. We don’t need it to understand who or what is being referred to.
We always use a relative pronoun (who, which, whose or whom) to introduce a non-defining relative clause (In the examples, the relative clause is in bold , and the person or thing being referred to is underlined.)
Clare, who I work with , is doing the London marathon this year.
Not: Clare, I work with, is doing the London marathon this year .
Doctors use the testing kit for regular screening for lung and stomach cancers, which account for 70% of cancers treated in the western world .
Alice, who has worked in Brussels and London ever since leaving Edinburgh , will be starting a teaching course in the autumn.
We don’t use that to introduce a non-defining relative clause:
Allen, who scored three goals in the first game , was the only player to perform well.
Not: Allen, that scored three goals in the first game, was the only player to perform well .
In writing, we use commas around non-defining relative clauses:
Spoken English:Etheridge, who is English-born with Irish parents , replaces Neil Francis, whose injury forced him to withdraw last week .
In speaking, we often pause at the beginning and end of the clause:
Unlike American firms – which typically supply all three big American car makers – Japanese ones traditionally work exclusively with one maker. (formal)
And this woman – who I’d never met before – came up and spoke to me. (informal)
Sometimes defining and non-defining relative clauses can look very similar but have different meanings.
His brother, who works at the supermarket , is a friend of mine.
He has only one brother, and that brother works at the supermarket.
His brother who works at the supermarket is a friend of mine.
He has more than one brother. The one I’m talking about works at the supermarket.
It’s hoped that we will raise £10,000 for local charities, which help the homeless .
The money is intended for local charities. All these local charities help the homeless.
It’s hoped that we will raise £10,000 for local charities which help the homeless .
The money is intended for local charities. Some of these local charities help the homeless. There are other local charities as well as these.
The information in a defining relative clause is essential, so we can’t leave out the relative clause. The information in a non-defining relative clause is extra information which isn’t essential, so we can leave out the relative clause.
The soldier who had gold stripes on his uniform seemed to be the most important one.
A defining relative clause which we can’t leave out; without this information we do not know which soldier the speaker is referring to.
The tour party was weakened when Gordon Hamilton, who played in the World Cup team , withdrew yesterday because of a back injury, which kept him out of the Five Nations Championship .
Non-defining relative clauses which we can leave out:
The tour party was weakened when Gordon Hamilton withdrew yesterday because of a back injury.
We can use that instead of who, whom or which in defining relative clauses, but not in non-defining relative clauses:
I think anyone who speaks in public is nervous beforehand.
I think anyone that speaks in public is nervous beforehand.
Her car, which was very old, broke down after just five miles.
Not: Her car, that was very old, broke down after just five miles .