Clauses in English language

                   A clause is a group of words that contains a verb (and usually other components too). A clause may form part of a sentence or it may be a complete sentence in itself. For example:

He was eating a bacon sandwich.

[Clause]

She had a long career     but she is remembered mainly for one early work.

[Clause]                                 [Clause]

Main clause

                   Every sentence contains at least one main clause. A main clause may form part of a compound sentence or a complex sentence, but it also makes sense on its own, as in this example:

He was eating a bacon sandwich.

[Main clause]

                 Compound sentences are made up of two or more main clauses linked by a conjunction such as and, but, or so, as in the following examples:

I love sport And I’m captain of the local football team.

[Main clause]      [Conjunction]              [Main clause]

She was born in Spain But Her mother is Polish.

[Main clause]   [Conjunction] [Main clause]   

 Subordinate clause

                   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: 

After we had had lunch 

.We went back to work.

[Subordinate clause]          [Main clause] 

I first saw her in Paris,

Where I lived in the early nineties.

[Main clause]               [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: 

If it looks like rain             a simple shelter can be made out of a plastic sheet

[Conditional clause]        [Main clause]

I'll be home tomorrow   unless the planes delayed for hours.

[Main clause]     [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: 

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

[Main clause]     [Relative clause]

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

[Main clause]     [Relative clause]

I was wearing the dress                that I bought to wear to Jo's party.

 [Main clause]    [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:

√ She held out the hand               which was hurt.

√ she held out the hand                that was hurt.

[Main clause]     [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.

[Main clause]     [Restrictive relative clause]

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:

She held out her hand,  which Rob shook.

[Main clause]     [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:

 Bill,         who had fallen asleep on the sofa,          suddenly roused himself.

                [Non-restrictive relative clause]