A clause is a group of words containing a subject and a verb. A clause can act as a simple sentence, e.g., He laughed. Likewise, a sentence can have more than one clause, e.g., I waited for him, but he didn’t come (two clauses).

Clauses can be classified into two major types: 1) Main or Independent Clause, and 2) Subordinate or Dependent Clause.

Example.

• I saw a man who was crying.

In the above sentence, ‘I saw a man,’ can stand alone as an independent sentence because it gives a complete meaning on its own. Such a clause is called the main clause or independent clause.

On the other hand, the remaining part of the sentence, ‘who was crying,’ cannot stand alone as a sentence because it (as a standalone part) cannot give a complete meaning. It depends on the main clause to give a complete meaning. Such a clause is called a dependent clause or subordinate clause.

A subordinate clause can function as a noun, adjective, or adverb in a sentence. Based on its function, there are three types:

• Noun Clause
• Adjective Clause
• Adverb Clause

A subordinate clause that acts as a noun in a sentence is called a noun clause.

It usually begins with words such as that, what, whatever, who, whom, whoever, whomever. A noun clause can function as the subject or object of a sentence. Examples:

• Whatever we study increases our knowledge.   (Noun as a subject).
• What you eat determines your body size.         (Noun as a subject).
• I buy whatever I need.     (Noun as an object).
• Now I realized what you had said.     (Noun as an object).
  

A subordinate clause that acts as an adjective in a sentence is called an adjective clause.

Like an adjective, it modifies (gives more information about) a noun or pronoun in the sentence. Adjective clauses usually begin with relative pronouns such as that, who, whom, whose, which.

Examples:

• I saw a child who was crying.                           (modifies noun: child).
• He hates the people who waste time.               (modifies noun: people).
• I watched a movie which amused me a lot.     (modifies noun: movie).
• The car, which I like, consumes less fuel.        (modifies noun: car).
• The building, where he lives, consists of many apartments. (modifies noun: building).

A subordinate clause that acts as an adverb in a sentence is called an adverb clause.

Like an adverb, it modifies a verb, an adjective, or another adverb. Adverb clauses provide more information about a verb in terms of time, frequency, condition, cause and effect, or intensity.

Adverb clauses usually begin with the following subordinating conjunctions:

• Time: when, whenever, since, until, before, after, while, as, by the time, as soon as
• Cause and effect: because, since, now that, as long as, so, so that
• Contrast: although, even, whereas, while, though
• Condition: if, unless, only if, whether or not, even if, providing/provided that, in case

Examples:

• Call me when you need my help.                            (modifies verb: call).
• Unless you avoid sugar, you can’t lose weight.     (modifies verb: lose weight).
• The patient had died before the doctor came.       (modifies verb: die).
• You live a happy life as long as you think positively.    (modifies verb: live).
• I worked in a factory while I was living in London.       (modifies verb: work).
• You can succeed in life provided that you are sincere in your work. (modifies verb: succeed).