There are four main types of sentence structures: simple, compound, complex, and compound-complex.

1. Simple sentence structure: A simple sentence consists of one independent clause, which contains a subject and a predicate. It expresses a complete thought and can stand alone as a sentence. For example: “She ran to the store.”

2. Compound sentence structure: A compound sentence consists of two or more independent clauses joined by a coordinating conjunction (such as “and,” “but,” or “or”) or a semicolon. Each independent clause expresses a complete thought. For example: “She ran to the store, and he stayed at home.”

3. Complex sentence structure: A complex sentence consists of one independent clause and at least one dependent clause. The independent clause expresses a complete thought, while the dependent clause relies on the independent clause to make sense. For example: “Although it was raining, she ran to the store.”

4. Compound-complex sentence structure: A compound-complex sentence consists of two or more independent clauses and at least one dependent clause. It combines the features of both compound and complex sentences. For example: “She ran to the store, but he stayed at home because it was raining.”

These sentence structures allow writers to vary their sentence lengths and structures, adding complexity and variety to their writing.