The comma splice is the femme fatale of the grammar world. It sounds sexy and even a little dangerous. But what is it?
A comma splice is what happens when you attempt to string together two independent clauses using only a comma. Independent clauses are complete thoughts; they consist of, at minimum, a subject and a predicate. The subject tells us who or what the sentence is about, and the predicate shows us what happens. Within that framework are endless permutations.
“Jane ate the lemon pie.”
“Jane, in a fit of pique, ate the entire lemon pie that her sister, Marguerite, had baked especially for her gentleman caller in an attempt to impress him with her culinary prowess.”
All of these, even the third example, are simple sentences because they contain one subject and one predicate apiece. A compound sentence has two of each–two complete thoughts–joined by either a semicolon or a comma plus a coordinating conjunction. Let’s look at an example:
“Jane ate the lemon pie; it was delicious.”
Both “Jane ate the lemon pie” and “it was delicious” are complete thoughts. Both contain a subject (“Jane” and “it,” respectively), and both contain a complete predicate. They could be written as separate sentences, but we want to demonstrate a relationship between them. The semicolon simply shows the reader that the two thoughts are linked, but it leaves it up to us to infer the nature of that relationship. It could be cause and effect, sequence, or comparison.
To make the relationship even clearer, we could use a coordinating conjunction. There are are seven coordinating conjunctions to choose from: For, And, Nor, But, Or, Yet, and So. (I remember them by the mnemonic FANBOYS.) Each of them describes a different relationship between the two clauses. We could probably use “and” or “for” in the example sentence:
“Jane ate the lemon pie, and it was delicious.”
“Jane ate the lemon pie, for it was delicious.”
What we can’t do, however, is use a comma to link the two independent clauses. That way lies the dreaded comma splice:
“Jane ate the lemon pie, it was delicious.”
If you’re faced with a potential comma splice, try separating the two halves of the sentence and reading them out loud. If they both make sense as separate sentences, then you need to add a coordinating conjunction or swap the comma for a semicolon.
If you’re still confused, I recommend turning to Sir Mix-a-Lot for guidance. In his classic hit song, he states, “I like big butts, and I cannot lie.” He correctly joined two independent clauses with a comma and coordinating conjunction. “I like big butts, I cannot lie” is not only a comma splice, but it ruins the rhythm of the song, too.