And why sometimes, it’s not even an error.
Why Are So Many People Confused About Comma Splices?
The examples I just gave are the simple kind of sentences you’ll see in most explanations of comma splices, but because they’re so simple, they don’t show you the whole problem.
Sometimes Participial Phrases and Clauses Can Look a Lot Alike
I was pondering why people have so much trouble identifying comma splices when I started browsing through a new book that had just arrived in the mail. Penguin sent me a copy of Brooks Landon’s Building Great Sentences, and it had a short, half-page section that answered the question perfectly: He points out that it’s exceedingly common for authors to put a phrase after a comma, and that’s not an error. It’s good writing style. A phrase is fine after a comma, but a lone clause is not; and many people (even English majors) don’t know the difference between a phrase and a clause. (1)
A clause can stand alone as a sentence, and a phrase cannot.
Here are examples of phrases that appropriately come after an independent clause and a comma:
It had started raining again, fat drops hitting the window like pebbles. (A Memory of Light, Robert Jordan & Brandon Sanderson)
It crouches low and creeps toward me, its lips peeling back from its white teeth. (Divergent, Veronica Roth)
Those parts that come after the comma are all phrases, participial phrases to be exact because they contain a participle—which is something that looks a lot like a verb, but isn’t. The important thing to note is that none of those phrases can stand alone as a sentence. Look at them:
Fat drops hitting the window like pebbles.
Its lips peeling back from its white teeth.
Those shouldn’t sound like sentences to you. They would be sentences if you replaced the participle with a real verb (fat droplets hit the window like pebbles, instead of hitting the window, for example), but they aren’t sentences or independent clauses as they are written. Even though they look like sentences, they’re actually phrases, which means they’re allowed to follow a clause and a comma. No comma splices here.
Next: More Examples and the Role of Appositives