A clause is a combination of related words containing a subject and a verb. It can be itself a simple sentence or a part of a compound sentence that has more than one clause. 

Examples.

• She is laughing.  (one clause)
• I waited for him, but he didn’t come.  (two clauses)

Clauses have two major types:

• Independent Clause (Main Clause)
• Dependent Clause (Subordinate Clause)

Read the following example.

• I saw a man who was crying.

The above sentence has two clauses: ‘I saw a man’ and ‘who was crying’. The first clause ‘I saw a man’ can stand alone as a complete sentence because it gives a complete meaning on its own. This is called the main clause (or independent clause) because it can stand alone as a sentence to give a complete meaning.

On the other hand, the second clause ‘who was crying’ cannot stand alone as a sentence because it cannot give complete meaning on its own. It depends on the main clause to give a complete meaning or sense. Such a clause is called a subordinate clause or dependent clause.

Main or independent clauses can stand alone as a sentence because it can express a complete meaning. It is called an independent clause because it is not dependent on the remaining part of a sentence to give a complete meaning. This means it can give a complete meaning even if written or spoken without the remaining part of the sentence. It is called the main clause because it provides a basis to the remaining part of the sentence (e.g., the subordinate clause) to complete meaning of the remaining part if written along with it. However, it itself can stand as a lone sentence and does not require the remaining part of the sentence for expression of its own meaning.  

Examples.

• I saw a man who was crying.
• The teacher asked a question, but no one could answer.
• I met a friend who helped me a lot.
• They contacted the customer who had not paid the bill.
• He does not like the people who smoke.
• We met a person who could speak many languages.
• She loves her husband, who never tells her a lie.

A subordinate or dependent clause cannot stand alone as a sentence because it (as an alone part) cannot express complete meaning or sense. It is called a dependent clause because it depends on the main clause to give a complete meaning. It is called a subordinate clause because it plays a subordinate role in relation to the main clause within a sentence.

Examples.

• I saw a man who was crying.
• The teacher asked a question, but no one could answer.
• I met a friend who helped me a lot.
• They contacted the customer who had not paid the bill.
• He does not like the people who smoke.
• We met a person who could speak many languages.
• She loves her husband, who never tells her a lie.

Note. Subordinate (or dependent) clauses have three types: 1) Noun clause, 2) Adjective Clause, and 3) Adverb clause. Click here to read them.