How to Use Commas
Commas are always tricky because there are so many different ways you can use them, but one of the most common ways to use commas is to separate two main clauses that are connected by a coordinating conjunction. That just means that when you join two things that could be sentences on their own with a word such as and, but, or or, you need a comma before the conjunction. For example
Squiggly ran into the forest to hide, and Aardvark realized he’d have to fight the peeves alone.
Squiggly ran into the forest to hide is a complete sentence, and Aardvark realized he’d have to fight the peeves alone is also a complete sentence. To join them with a comma, you need the word and or some other coordinating conjunction. If you just put a comma between them without a conjunction, that’s an error called a comma splice or a comma fault. Here’s an example:
Squiggly ran into the forest to hide, Aardvark realized he’d have to fight the peeves alone. (wrong)
What Is a Comma Splice?
It’s easy to see in that example why the error is called a comma splice because I’m using a comma to splice together two complete sentences when that isn’t a comma’s job.
Commas aren’t meant to join main clauses all by themselves; when you force them into that role, you make an error called a comma splice.
The good news is that it’s easy to fix the problem. For example, because the two clauses are complete sentences by themselves, you can treat them that way and use a period where you had a comma.
Squiggly ran into the forest to hide. Aardvark realized he’d have to fight the peeves alone.
It is a period’s job to separate complete sentences.
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