An independent clause or main clause is a group of words that include a subject and a verb. It is a complete sentence that expresses a complete thought. This means it can stand alone as it is not dependent on another clause to form a sentence. A sentence must have a main clause.
The following are complete statements and are therefore main clauses.
- All of us sat beneath a shady tree.
(Subject: All of us; action verb: sat)
- You are my best friend.
(Subject: You; linking verb: are)
- My uncle has a mongoose with a long body and tail.
(Subject is my uncle. The verb has can be an action verb or a linking verb. It is used here as a linking verb.).
Each of the following is a group of words that does not qualify as an independent clause. Each one is an incomplete statement and it cannot stand on its own as an independent clause.
- That you are my best friend
(This is not an independent clause. It is a that-clause introduced by the relative pronoun that.)
- When all of us sat beneath a shady tree
(The relative pronoun when introduces a relative clause. A relative clause is a dependent clause.)
- My uncle who has a male mongoose with a long body and tail
(The subject my uncle is followed by the relative clause who has a male mongoose with a long body and tail. The subject must be followed by at least a verb to make a complete clause/sentence.)
Correction of the incomplete statements above
- They said that you are my best friend.
(They said is a main clause joined to the that-clause fo form a complete sentence.)
- When all of us sat beneath a shady tree, we could feel the soft cool grass.
(The main clause we could feel the soft cool grass is depended on by the relative clause to form a complete sentence.)
- My uncle, who has a male mongoose with a long body and tail, is looking for a female mongoose.
(The relative clause is within the main clause which is My uncle is looking for a female mongoose.)