Every sentence contains one main clause. A complex sentence contains one main clause and one or more subordinate (less important) clauses.
Example: Milo is happy when he rides his bicycle.
A complex sentence has an main or independent clause (a clause in a sentence that can stand on its own) and a subordinate or dependent clause ( a clause that is not a complete sentence; it cannot stand on its won). Observe the sentence below and you will notice that a dependent clause starts with so, because, since, etc.
Example: The boy is happy because he got a new bicycle.
The dependent clause “he got a new bicycle” starts with because.
Now, it is time for some exercises.