Relative clauses add extra information to a sentence by defining a noun. They are usually divided into two types –defining relative clauses and non-defining relative clauses.
A relative clause is one that adds information to a sentence, in relation to a noun. For example, in the sentence “I will buy the car that costs the least.” Relative clauses can be connected to sentences by relative pronouns, who, which, that, whom and whose. There are a variety of grammar rules to tell you which relative pronoun to use for a relative clause, but in popular English, it has become possible to use that for a large number of relative clauses. However, there are still times when you cannotuse that.
Who, Which or That
When connecting relative clauses, we use who or whom for people, and which for things (essentially, for everything else).
- She is the girl who I want to marry. / She is the girl that I want to marry.
- Here is the pen which I want to buy. / Here is the pen that I want to buy.
These examples use defining relative clauses; they define the noun by telling us who or which noun it is specifically (in these cases, defining her as one particular girl, or defining the pen as one particular pen). If you remove the defining relative clause from the sentence, then we might not understand who or which noun is being spoken about.
With defining relative clauses, it is possible to use that in place of who or which, for people or things.
Non-defining relative clauses
With non-defining relative clauses, that cannot be used. Consider the following examples:
- My uncle, who served in the army, is a very brave man.
- This pen, which I bought two days ago, has stopped working.
In both of these examples, using that would not be appropriate (e.g. This pen, that I bought two days ago…). This is because the sentences use non-defining relative clauses. They add extra information to the sentence, but that information does not define the noun. The sentences would have the same meaning without the relative clauses.
- My uncle is a very brave man.
- This pen has stopped working.
Non-defining relative clauses do not tell us who or which noun the subject is, they merely add information about the subject.
How to check if a relative clause is defining or not
Non-defining relative clauses are used between commas in the middle of a sentence.
- The boy’s first exam, which was difficult, took him a long time to complete.
In this sentence, the noun “exam” is defined by “first”; we already know which exam. The non-defining clause only tells us more about it. Consider the difference here:
- It was the exam which he had to pass.
In this case, the relative clause defines the noun, as it tells us which exam it is – the one he had to pass. As a defining relative clause answers the question “Who?” or “Which one?”, a relative clause will be defining or non-defining depending on if its information answers that question. Consider one more example:
- My office, which is on the third floor, is very hot. (non-defining)
- The office which is on the third floor is very hot. (defining)
In the first example, the non-defining relative clause gives extra information about a noun that is already defined (Which office? – my office) – in the second example, the relative clause is what tells us which office (the one on the third floor).
To help you practice identify if a relative clause is defining or non-defining, (and therefore to know whether or not you can use that) try the exercise below.
Defining or non-defining relative clauses exercise
With the following situations, you can choose between a sentence with a defining or non-defining relative clause. The additional information before the sentences will help you decide which is the most appropriate.
- I have two cats.
- My cat which is in the garden is very relaxed.
- My cat, which is in the garden, is very relaxed.
- He has one brother.
- His brother who works in the city has a new car.
- His brother, who works in the city, has a new car.
- Bill’s father has moved to Brighton.
- Bill’s father who is 65 years old has moved to Brighton.
- Bill’s father, who is 65 years old, has moved to Brighton.
- I have one sister.
- My sister who is going to work in Hong Kong is learning Chinese.
- My sister, who is going to work in Hong Kong, is learning Chinese.
- She has six cousins.
- Her cousin who got married last week is going to Bali.
- Her cousin, who got married last week, is going to Bali.
- A man is moving.
- The man who lives at number 23 is moving out.
- The man, who lives at number 23, is moving out.
- I have just seen a film.
- The film which stars Brad Pitt is good fun.
- The film, which stars Brad Pitt, is good fun.
- Tina has two large dogs.
- Tina’s dogs which are rather big need to go for long walks.
- Tina’s dogs, which are rather big, need to go for long walks.
- Jane has one large dog and one small one.
- Jane’s dog which is big needs to go for long walks.
- Jane’s dog, which is big, needs to go for long walks.
- Discussing Brighton Pavilion.
- Brighton Pavilion which is near the seafront is a beautiful building.
- Brighton Pavilion, which is near the seafront, is a beautiful building.
Defining and Non-Defining Relative Clauses Exercise Answers
The answers to this exercise are as follow, with either D (defining) or ND (non-defining relative clauses).
Remember, that can only be used to join the defining relative clauses! As always, if you have any questions, please let me know, and if you enjoyed this article please do share it.