complex sentence noun2 •A sentence that contains an independent clause as well as one or more dependent clauses, such as a relative clause, an adverbial clause, or a noun clause. •A sentence that contains multiple clauses, whether independent (coordinated) or dependent (subordinated); compound or complex sentence.Complex sentences are traditionally divided into two basic types: (i) sentences including co-ordinate clauses, and (ii) sentences including subordinate clauses. — 2004 formscomplex sentences