Restrictive & Non-Restrictive Clauses

The park that we visited last week was very crowded.

In the above sentence the bolded parts describe the type of park we visited. It describes the park – the subject of the sentence – that we visited last week. Therefore it is termed an adjectival clause or a relative clause, because it relates to the noun that the adjectival clause modifies.

If we look at the sentence that we visited last week is important to the meaning of the sentence.  It limits and modifies the type of park we visited.

Q:which park was very crowded?

A:the one that we visited last week.

Let us take another example:

The train which was newly introduced attracted a lot of passengers.

In the above sentence the bolded parts describe the type of train that attracted a lot of passengers

If we look at the sentence which was newly introduced is important to the meaning of the sentence.  It limits and modifies the type of train which attracted a lot of passengers.

In both the cases, the bolded parts are essential to the meaning of the sentence and modify the noun that precedes them. Hence these clauses are termed restrictive clauses as they restrict the meaning of the noun that precedes them.

Restrictive clauses can begin with – that, which, who, whom, whose.

The person who called me yesterday was my brother.

The lady whom I mentioned in my letter was my school teacher.

The policeman whose car was damaged in a crash is a going after the suspect.

The park that we visited last week was very crowded.

The train which was newly introduced attracted a lot of passengers.

However, there are sentences in which the relative clause merely provides additional information about the noun, but does not modify, limit or restrict the noun. For example:

My sister, who lives in Canada, is a doctor.

Here who lives in Canada only provides additional information and does not modify sister. The sentence would still be meaningful if you eliminate who lives in Canada.

My sister, who lives in Canada, is a doctor.

My sister is a doctor (still meaningful).

We can see that the second sentence above still makes perfect sense. It does not lose its meaning when we remove the relative clause. Such relative clauses are called non-restrictive clauses, because they do not modify, limit or restrict the subject (my sister) of the sentence.

And to show that they merely provide extra information, we surround the clause with a comma.

The bike, which was stolen yesterday, was recovered by the police.

which was stolen yesterday provides additional information, and does not modify the type of bike. So we surround them with commas.

The lady, whom you saw yesterday, is my wife.

The aircraft, whose propeller was damaged, landed in Geneva.

In all the above examples, who, which, whom & whose, provide additional information, and are therefore surrounded by commas and are known as non-restrictive clauses.

However, that can never be used in a non-restrictive clause.

that is always used in a restrictive clause. It is never used in a non-restrictive clause

Non-Restrictive clauses can begin with – which, who, whom, whose.

The same clause can be both restrictive or non-restrictive.

My sister, who lives in Canada, is a doctor

who lives in Canada is a non-restrictive clause. It provides additional information.

The sentence does not lose its meaning when we remove the relative clause

But if we write it as:

My sister who lives in Canada is a doctor

who lives in Canada is a restrictive clause as it describes the subject (sister). I have many sisters and the sister who lives in Canada is a doctor. (note: we did not use commas as it modifies the subject). The sentence we lose its meaning if we drop the clause.