Complex Sentences
A complex sentence is one which contains not only a main assertion (or more than one), but also one or more subordinate assertions—that is, it contains one or more assertions which are grammatically incorporated as a noun or an adjective or an adverb into the main clause or into another subordinate clause.
I saw that he had finished.
Heavy automobiles which carry large loads run smoothly.
The weather will be what fate determines.
He broke the stone that he might find a fossil.