The main clause is a group of words that include a subject and a finite verb. It is not a part of another clause, or dependent on another clause to form a sentence. It can stand independently as it makes a complete statement. A sentence must have a main clause.

 

Each of the following is a group of words that does not qualify as a main clause as they are incomplete statements and so cannot stand on their own.
  • That you are my best friend.
  • When all of us sat beneath a shady tree.
  • My uncle who has a mongoose with a long body and tail.

 

The following are complete statements and are therefore main clauses.
  • You are my best friend.
  • All of us sat beneath a shady tree.
  • My uncle has a mongoose with a long body and tail.