A simple sentence, also called an independent clause, can stand alone as a sentence. A dependent clause cannot stand alone. We form a complex sentence when we connect an independent clause to a dependent clause in one complete sentence. Read on to learn how to write complex sentences.
Add a subordinating conjunction to the dependent clause. Frequently used subordinating conjunctions include after, if, once, unless, when, since and because.
Place a comma after the dependent clause when making a complex sentence. For example, "Although I drove all day, I am not tired." The word "although" is a subordinating conjunction. Note that the part of the sentence with the subordinating conjunction is a dependent clause and the part of the sentence after the comma is an independent clause.
Leave out the comma when the subordinating conjunction comes after the dependent clause. For example, "I am tired after driving all day." Note that the clause that follows the subordinating conjunction ("after") is a dependent clause, not a complete sentence.
Use a relative pronoun to form a complex sentence. Some examples of relative pronouns include that, which, whose and what. The relative pronoun introduces a dependent clause and describes a noun or a pronoun. For example, "I got a score of 10, which is the highest score you can get." The first part of the sentence, the independent clause, can stand on its own, and the second part of the sentence adds information.