A compound sentence is made up of two complete thoughts joined together with a coordinating conjunction.
Each complete thought is a simple sentence, so two simple sentences make a compound sentence.
Join two simple sentences with a comma and one of the FANBOYS – for, and, nor, but, or, yet, so – to make a compound sentence.
When you use the conjunction and, you can switch the two independent clauses and the sentence still makes sense.
I have a pet dog, and my sister has a pet turtle.
My sister has a pet turtle, and I have a pet dog.
Even though we switched the order of the two clauses, the sentence means basically the same thing.
We can sometimes switch the order of the clauses when we use the conjunction or.
I can bring a cake to the party, or I can bring some cookies.
I can bring some cookies to the party, or I can bring a cake.
Both of these sentences say the same thing even though we changed the order.
However, there is another way to use or – when it means or else.
I should probably eat dinner now, or it will be too late.
We can’t rearrange these clauses without making the sentence sound ridiculous: It will be too late, or I should probably eat dinner now.
The order of the clauses used with the conjunctions but or yet can usually be switched.
I like cookies, but my sister likes cake. OR My sister likes cake, but I like cookies.
The sun is still shining, yet it’s late. OR It’s late, yet the sun is still shining.
When you use so and for to make a compound sentence, you cannot rearrange the order of the clauses.
I’m hungry, so I will make dinner.
We can’t say I will make dinner, so I’m hungry. This doesn’t make any sense.
Tom is feeling happy, for he got his first perfect score in bowling.
We can’t say He got his first perfect score in bowling, for Tom is feeling happy. It doesn’t make any sense.
When you use one of the FANBOYS to join two simple sentences, sometimes the clauses in the compound sentence can be rearranged, and sometimes there is only one way to write the sentence so it makes sense.