Clause and Its Types

The expression of a complete proposition by smallest grammatical unit is known as clause. Basically, a clause contains both predicate and subject. There could be one or more than one clauses in the sentence. A sentence that consists of just one clause is known as a simple sentence. For example: I went New York. She liked Mexico. There are various types of clause which are explained below:

Coordinate Clauses

A sentence which consists of 2 clauses and joined by conjunctions such as: or, and, etc. These clauses are known as coordinate clauses and sentence with these clauses is called compound sentence.  
For example: Bobby went for fishing and Shan liked cow.

Subordinate Clauses

Subordinate clauses have a verb and a subject, but do not make any sentence by themselves. These clauses usually start with words such as: because, if, who, when, even, unless, while, etc. Usage of these words depends on the subordinate and main clause.
For example: Unless George completes his assignment (subordinate clause), he will have to stay (main clause)

Adverbial Clause of Concession

A subordinate clause that tells you something surprising connected with the main clause is called adverbial clause of concession or contrast.
For example: He has decided to retire, although he is only 55.

Adverbial Clause of Time

Adverbial clause of time is also a subordinate clause that tells about time of action in the main clause. This type of clause starts with before, since, while, etc. 
For example: Prepare yourself before exams.

Adverbial Clause of Reason

A subordinate clause that gives the reason for the action in the main clause is known as adverbial clause of reason.
For example: John was absent, because he was ill.

Adverbial Clause of Purpose

A subordinate clause that tells the purpose of the action in the main clause is known as adverbial clause of purpose. 
For example: They are working hard, so that they will do well in the exam.