- The definition of a complex sentence is the joining of an independent clause and one or more dependent clauses.
An example of a complex sentence is, "When I finish my homework, I will start baking the cookies."
complex sentence definition by Webster's New World
complex sentence - Cultural Definition
A sentence that contains one main clause or independent clause and at least one subordinate clause or dependent clause: “Although I am tired (subordinate clause), I want to go to the midnight movie (main clause).” (See subordination; compare compound sentence, compound-complex sentence, and simple sentence.)