Once you learn about comma splices, you notice them everywhere, and a listener named Jo has started noticing them. She wrote, “Comma splices are the rage on the internet these days. Can you write about them sometime?” Well, I have written about them, but it was four years ago, so it’s definitely time for a refresher.

@GrammarGirl Comma splices are the rage on the internet these days. Can you write about that sometime?

— Jo Alexander (@FashionSpire) May 18, 2016

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.

How to Use a Semicolon to Fix a Comma Splice

If the two sentences are closely related to each other, you can use semicolon to fix a comma splice. For example, if we imagine that Squiggly and Aardvark were in the woods when their campsite was attacked by monsters called peeves and we’re describing our two characters’ reaction to the attack, you can use a semicolon to connect the two parts without a coordinating conjunction.

Squiggly ran into the forest to hide; Aardvark realized he’d have to fight the peeves alone.

The semicolon makes sense because the second clause is related to the first clause. Aardvark knows he has to fight the peeves alone because Squiggly has run off into the forest and is going to be useless. (Want more? See Episode 189, How to Use Semicolons.)

You can think of a semicolon as a “sentence splicer” because its job is to splice complete sentences together. It’s stronger than a comma.

How to Use Coordinating Conjunctions to Fix a Comma Splice

You can also usually fix a comma splice by adding a coordinating conjunction.

If I go back to the original sentence with a comma splice—Squiggly ran into the forest to hide, Aardvark realized he’d have to fight the peeves alone—you can see that it makes sense to connect those two sentences with a coordinating conjunction and a comma.

Squiggly ran into the forest to hide, and Aardvark realized he’d have to fight the peeves alone.

Turn a Main Clause into a Subordinate Clause

Our comma splice repair kit includes periods, semicolons, and coordinating conjunctions. That’s pretty standard, but you can also fix comma splices other ways too. For example, you can make one of the main clauses a subordinate clause. I could write

Because Squiggly ran into the forest to hide, Aardvark realized he’d have to fight the peeves alone.

Now you can join them with a comma because one clause is a main clause and the other is a subordinate clause. And yes, you can start a sentence with the word because when it’s the start of a subordinate clause. If the subordinate clause comes before the main clause, like it just did, you put a comma after it, but if the subordinate clause comes after the main clause, you don’t use any punctuation at all.

Aardvark realized he’d have to fight the peeves alone because Squiggly ran into the forest to hide.

You can read more about subordinating conjunctions in Episode 221, ‘Although’ Versus ‘While,’ and in the tip Can You Start a Sentence with “Because”?

Turn One Clause into a Phrase

This final approach won’t work with the example sentence we’ve been using so far, but sometimes you can also turn one of your main clauses into a phrase. Consider this comma splice example:

Aardvark has a black belt in Judo, he realized he would have to fight the peeves alone. (wrong)

You could fix that in the ways we’ve already talked about, but you could also pull out the “black belt” part into a phrase that is surrounded by dashes, parentheses, or commas, like this:

Aardvark–a black belt in Judo–realized he would have to fight the peeves alone.

Aardvark (a black belt in Judo) realized he would have to fight the peeves alone.

Aardvark, a black belt in Judo, realized he would have to fight the peeves alone.

Occasionally, Comma Splices Are OK

Finally, now that I’ve shown you a bunch of ways to get rid of a comma splice, I should also tell you that occasionally, in rare specific cases, they are also OK. Yes, I just said comma splices are allowed in some cases. For example, the authors of the grammar handbook Things Your Grammar Never Told You say it is acceptable to use commas to join very short sentences that are exactly parallel: I came, I saw, I conquered. You’ll find similar advice in The Elements of Style, but also remember these kinds of sentences don’t come up in real life very often.

Comma Splice Summary

The next time you catch yourself in a comma splice, dig through your toolbox to see if you can fix it with a period, a coordinating conjunction, or a semicolon; and if that doesn’t work, try more serious rewriting such as turning one part into a subordinate clause or parenthetical phrase. Commas aren’t meant to join main clauses all by themselves, but fortunately, a comma splice is easy to fix.

Exercises

Fix the comma splices in the following sentences. Try to use each of the following: a semicolon, a coordinating conjunction, a period, turning part of the sentence into a subordinating conjunction, and turning part of the sentence into a parenthetical phrase.

• 1. Please pick up a lime at the store, I need it for the guacamole.
• 2. Mariana broke her leg skiing, she didn’t finish her homework.
• 3. Spencer groomed all 10 dogs in one day, he’s the most efficient groomer in the shop.
• 4. We called the DJ, we wanted to book him for the party.
• 5. I cooked dinner, Sarah did the dishes.
• 6. I ran all the way across campus to register for summer session, they were closed by the time I got there.