What is a complex sentence?
A complex sentence is a sentence that has one main clause and at least one subordinate or dependent clause.
A compound sentence is a sentence that has two or more main clauses.
A subordinate clause in a complex sentence is a clause that does not express the main idea of the entire sentence but rather expresses an idea that clarifies or provides additional information about the main clause.
Some examples of complex sentences are:
1) I went to school with my friend, who was eager to take the test.
2) I did not have to wait for the bus because my friend brought his car.
Some examples of compound sentences are:
1) I went to school with my friend; however, he was not eager to take the test.
2) I called my friend today, but he did not answer the phone.
https://www.notesflux.com/2017..../07/what-are-complex