A subordinate clause depends on a main clause for its meaning. Together with a main clause, a subordinate clause forms part of a complex sentence. Here are two examples of sentences containing subordinate clauses:
Example: After we had had lunch, we went back to work.

• After we had had lunch, [subordinate clause]
• we went back to work. [main clause]

Example: I first saw her in Paris, where I lived in the early nineties.

• I first saw her in Paris, [main clause]
• where I lived in the early nineties. [subordinate clause]

Types of Subordinate Clause

There are two main types of subordinate clause:

• conditional clauses and
• relative clauses.

Conditional Clause

A conditional clause is one that usually begins with if or unless and describes something that is possible or probable:
Example: If it looks like rain a simple shelter can be made out of a plastic sheet.

• If it looks like rain [conditional clause]
• a simple shelter can be made out of a plastic sheet. [main clause]

Example: I’ll be home tomorrow unless the plane delayed for hours.

• I’ll be home tomorrow [main clause]
• unless the plane’s delayed for hours. [conditional clause]

Relative Clause

A relative clause is one connected to a main clause by a word such as which, that, whom, whose, when, where, or who:
Example: I first saw her in Paris, where I lived in the early nineties.

• I first saw her in Paris, [main clause]
• where I lived in the early nineties. [relative clause]

Example: She wants to be with Thomas, who is best suited to take care of her.

• She wants to be with Thomas, [main clause]
• who is best suited to take care of her. [relative clause]

Example: I was wearing the dress that I bought to wear to Jo’s party.

• I was wearing the dress [main clause]
• that I bought to wear to Jo’s party. [relative clause]

Using Relative Clauses: Have you ever wondered about when to use that and when to use which or who in this type of sentence? In fact, for much of the time that is interchangeable with either of these words. For example:

• You’re the only person who has ever listened to me.
• You’re the only person that has ever listened to me.
• It’s a film that should be seen by everyone.
• It’s a film which should be seen by everyone.

When referring to something, rather than someone, that tends to be the usual choice in everyday writing and conversation in British English.

However, there is one main case when you should not use that to introduce a relative clause. This is related to the fact that there are two types of relative clause:

• a restrictive relative clause and
• a non-restrictive relative clause.

Restrictive Relative Clause

A restrictive relative clause (also known as a defining relative clause) gives essential information about a noun that comes before it: without this clause the sentence wouldn’t make much sense.

A restrictive relative clause can be introduced by that, which, whose, who, or whom. You should not place a comma in front of a restrictive relative clause:
Example: She held out the hand which was hurt.

• She held out the hand [main clause]
• which was hurt. [restrictive relative clause]

Example: She held out the hand that was hurt.

• She held out the hand [main clause]
• that was hurt. [restrictive relative clause]

You can also leave out that or which in some restrictive relative clauses:

• It reminded him of the house that he used to rent in Oxford.
• It reminded him of the house which he used to rent in Oxford.
• It reminded him of the house he used to rent in Oxford.

 Non-restrictive Relative Clause

A non-restrictive relative clause (also called a non-defining relative clause) provides extra information that could be left out without affecting the meaning or structure of the sentence.

Non-restrictive relative clauses are normally introduced by which, whose, who, or whom, but never by that. You should place a comma in front of them:
Example: She held out her hand, which Rob shook.

• She held out her hand, [main clause]
• which Rob shook. [non-restrictive relative clause]

If a non-restrictive relative clause is in the middle of a sentence, you should put commas before and after it:
Example: Bill, who had fallen asleep on the sofa, suddenly roused himself.

• who had fallen asleep on the sofa [non-restrictive relative clause]

Thanks for reading about “types of subordinate clause”.