Simple sentences are sentences that contain only one independent clause. They express a complete thought and usually have a subject and a verb. For example, “The cat is sleeping.”

Compound sentences are sentences that contain two or more independent clauses joined together by a coordinating conjunction (such as “and,” “but,” or “or”) or a semicolon. Each independent clause in a compound sentence can stand alone as a complete sentence. For example, “I like to play soccer, and my brother likes to play basketball.”

Complex sentences are sentences that contain one independent clause and at least one dependent clause. A dependent clause cannot stand alone as a complete sentence because it does not express a complete thought. It relies on the independent clause to make sense. For example, “Although it was raining, we still went to the park.”

Compound-complex sentences are sentences that contain two or more independent clauses and at least one dependent clause. They combine the features of both compound and complex sentences. For example, “I went to the store, but I forgot to buy milk because I was in a hurry.”

It is important to note that the use of different sentence types can add variety and complexity to writing. Middle school students should practice using a variety of sentence structures to make their writing more interesting and engaging.