We talked yesterday about a grammar error called a comma splice. It is a mistake to use a comma between two simple sentences. Each simple sentence is a complete thought and must end with a period.
Comma splice error (run-on sentence): It looks like it may rain, I brought an umbrella.
Put a period between the two complete thoughts: It looks like it may rain. I brought an umbrella.
There is another way to punctuate two related simple sentences.
If the two simple sentences seem to go together, you can join them with a comma and one of the FANBOYS.
The FANBOYS are seven words that act as conjunctions. Conjunctions are joining words.
F = for
A = and
N = nor
F = for
B = but
O = or
Y = yet
S = so
Here are the same two sentences joined with a comma and one of the FANBOYS:
It looks like it may rain, so I brought an umbrella.
Look at these other examples:
I have a red bike. My sister has a green one.
I have a red bike, and my sister has a green one.
My dog is friendly. My cat ignores all my friends.
My dog is friendly, but my cat ignores all my friends.
Remember – We use a period after each complete thought. If you have two complete thoughts that seem to go together, you can join them into one sentence, but don’t put only a comma between the two complete thoughts. You must use a comma and one of the FANBOYS if you join two simple sentences together.