A simple sentence contains one main clause and no subordinate clauses. It expresses a complete thought and typically has a subject and a predicate. It does not contain coordinating conjunctions that connect two independent clauses (which would form a compound sentence).
For example:
- "The cat sleeps."
In contrast, a compound sentence consists of two or more independent clauses joined by coordinating conjunctions (like "and," "but," or "or"), while a complex sentence contains one main clause and one or more subordinate clauses.
So to summarize, a simple sentence has only one main clause.