Here's why:
* Connecting Ideas: Compound sentences are joined by coordinating conjunctions (like "and," "but," "or," "so," "for," "nor," "yet"). These conjunctions indicate a relationship between the two independent clauses.
* Showing Cause and Effect: A conjunction like "so" can show a cause-and-effect relationship between the clauses.
* Providing Contrast: Conjunctions like "but" and "yet" introduce contrasting ideas.
* Adding Information: Conjunctions like "and" and "or" often add more information to the first clause.
Example:
* The sun was shining, and the birds were singing. (Both clauses describe a pleasant scene.)
Exceptions:
While related thoughts are common, compound sentences can sometimes combine unrelated ideas.
Example:
* I went to the store, and the cat ate the mouse. (These clauses seem unrelated.)
In general, the coordinating conjunction used in a compound sentence often provides clues about the relationship between the ideas in the clauses.