In grammar, clause structure refers to the classification of sentences based on the number and kind of clauses in their syntactic structure. Such division is an element of traditional grammar.A simple sentence consists of only one clause. A compound sentence consists of two or more independent clauses. A complex sentence has at least one independent clause plus at least one dependent clause.A sentence consisting of one or more dependent clauses plus two or more independent clauses may be called a complex-compound sentence or compound-complex sentence.Sentence 1 is an example of a simple sentence. Sentence 2 is compound, while sentence 3 is complex.