Clause is a group of words that includes a subject and a verb. It may be a sentence or the part of a sentence.

There are three kinds of clauses:

1. Noun clause
2. Adverbial clause
3. Relative clause.

Noun Clause:

The that-clause following the main clause ‘I hope’ is also a noun clause just as ‘What I want’ is a noun clause which follows the main clause ‘she knows’.

Noun clauses begin with the following connectives:

1. Pronouns: what, which, who, whom, whose.
2. Adverbs: when, where, why, how.
3. Conjuctions: if, that, whether.

Functions of Noun Clauses:

Noun clauses function like nouns or noun phrases. They can function as subject, object, complement, or object of a preposition, etc:

Object of Preposition:

Example:

• You should pay attention to what the teacher says.
• There is no complaint except that he comes late.
• There is no meaning in what he says.
• No one is aware of how he has opened the lock.
• Everything depends on whether he helps us or not.
• It was difficult to decide on where we should go for help.
• They couldn’t agree about who should do the work.

Complement of an Adjective:

Example:

• I am not sure where he has gone.
• They are confident that they will find out the thief.
• It is doubtful whether she will reach in time.

Object of an Infinitive:

Example:

• She wants to know what is going on here.
• He came to see that he was mistaken.
• She wanted to ask if l could help her.

In A position to a Noun (Noun + Noun clause)

Example:

• The rumour that he was killed is true.
• The idea that we should set up a factory should be pursued.
• The fact that he has failed surprised his parents.

Object of a Participle:

Example:

• Thinking that he would die, they took him to a hospital.
• Hoping that they would win, they felt overjoyed.

Adverbial Clauses of Condition:

The adverbial clause of condition is introduced by if, unless, whether:

Example:

• If you run fast, you will catch the train.
• Unless you work hard .you will not pass.

The underlined words in the above sentences form the adverbial clauses of condition. A conditional clause is a subordinate clause and expresses a condition.

The conditional clauses are of the following types:

In an if-clause referring to a likely or possible situation in the future, the simple present tense is used. The future tense is used in the main clause:

Example: If it rains, we’ll go indoors.

Generally the main clause has the form: shall/will/may/can/must + first form of the verb:

Example:

• If she works hard, she will pass.
• If you request me, I shall help you.
• If you need a pen, you can take mine.
• If you want to get good marks, you must work harder.

In an if-clause referring to a condition that always has the same result, the simple present is used. The simple tense is used in the main clause too:

Example:

• If the engine gets too hot, it starts to smoke.
• If you heat ice, it melts.
• If you boil water, it evaporates.
• If you beat a child, he weeps.

If a conditional clause refers to an unlikely or impossible situation in the present or future, the simple past tense is used. In the main clause, we use should, could, might, would, etc + first form of the verb:

Example:

• If you ran fast, you might catch the train.
• If I won a lottery, I would buy a car.
• I would tell you if I knew the answer.
• If a thief entered your house, what would you do?
• If I were rich, I would open a school for the poor.