A simple sentence is a sentence that had one subject part and one predicate part.
A compound sentence is a sentence that contains two or more simple sentences joined by and, or, or but.
A compound subject has two or more simple subjects that have the same predicate. The subjects are joined by and.
A compound predicate is a predicate that has two or more verbs with the same subject. The verbs are connected by and or or.
In a compound sentence, use a comma before and, or, or but when they join simple sentences.
In a series of three or more nouns or verbs, use commas to separate them.