A comma ( , ) is a piece of punctuation used to force a pause or show a separation.
A compound sentence uses a coordinating conjunction to join two complete thoughts.
In a compound sentence, a comma must come before the conjunction.
FANBOYS is an acronym for the first letter of each coordinating conjunction.
F – for
A – and
N – nor
B – but
O – or
Y – yet
S – so
Anytime you use one of these seven coordinating conjunctions to join two complete thoughts together into one sentence, you must put a comma just before the conjunction. Look at these sentences examples:
I took my umbrella, for it looks as though it might rain.
John plays soccer, and his sister is the coach.
Sara doesn’t eat vegetables, nor does she like milk.
I can help you today, but I have to leave by 5:00.
I must be home for dinner, or I’ll end up getting in trouble.
Janet has a nice dress for the prom, yet she still isn’t sure about her shoes.
The dog got out of the yard, so I have to go find him.
Anytime you join two complete thoughts together into one sentence using a conjunction, you must use a comma just before the conjunction. We say to ourselves “comma, fanboys” when we are writing a compound sentence.