A simple sentence contains only one clause. A simple sentence may consist of only one word, such as "Go!" A simple sentence can also be longer in length, such as, "Mary went to the store to buy her mother cough medicine." Most people speak in simple sentences when talking to others.
A compound sentence contains at least two independent clauses, along with a conjunction, such as "but" or "and." The following examples are compound sentences: "I asked her to go to the movies, but she already had plans." "Sarah came to my house, and I showed her my new necklace."
A complex sentence consists of one independent clause and at least one dependent clause. The following is an example of a complex sentence: "While I like her new haircut, I prefer her hair longer." The word "while" is a clue that the opening clause is dependent on the second part of the sentence.
A compound-complex sentence consists of at least one dependent clause and at least two independent clauses. The following is an example of a compound-complex sentence: "My mother is strict about my grades in school, and my dad is more understanding when I receive a bad grade." The dependent clause, "when I receive a bad grade," occurs within the second independent clause.