5 of the Most Common Comma Mistakes

Monday, August 303 min read

The comma is a tiny punctuation mark that packs a lot of punch. Commas separate parts of a sentence, such as clauses or items. They can indicate pauses or just help to clear up the meaning of a phrase. However, it’s easy to get confused when it comes to setting commas in just the right place. From comma splices to serial commas, we review some of the most common comma errors.  

Introductory Words

Let’s start at the very beginning. When starting a sentence with a dependent clause or introductory word, use a comma.

No, I don’t want any pie.

On Tuesday, Mark is coming over.

Depending on the weather, we’re going to the beach.

Commas can often indicate a short pause, and that’s what’s happening here. The comma also subtly signals to the reader that the introductory part of the sentence is over.

A comma here also helps avoid confusion. Take the sentence, “After eating, my brother went home.” Without the comma, the sentence has an awkward start with “After eating my brother...” Luckily, the comma indicates the brother left.

Comma Splice

When a comma connects two independent clauses with no coordinating conjunction in between, it’s called a “comma splice.”

Diana went to the movies, she bought popcorn.

The comma separates the two halves of the sentence, but each of these halves could stand independently. For example, “Diana went to the movies” and “She bought popcorn” each make grammatical sense as statements by themselves. That means they don’t need to be linked together by the comma.

There are several ways to fix a comma splice. The first way is by adding a coordinating conjunction (for, and, nor, but, or, yet, so):

Diana went to the movies, and she bought popcorn.

The comma could be changed to a semicolon:

Diana went to the movies; she bought popcorn.

Finally, each independent clause could be its own sentence:

Diana went to the movies. She bought popcorn.

Oxford Comma

Also known as the “serial comma,” the Oxford comma is the sometimes-optional final comma in a list of things. For example, the comma after “milk” in the below sentence:

Gordon bought bread, milk, and eggs at the grocery store.

Some style guides insist on the Oxford comma, and others think it’s no big deal. But, neglecting to use it can lead to some serious misunderstandings.

I’m having breakfast with my parents, Beyoncé and Jay-Z.

The lack of an Oxford comma in this sentence makes its meaning ambiguous. Is the speaker having breakfast with four people — Mom, Dad, Beyoncé, and Jay-Z? Or are their parents actually Beyoncé and Jay-Z? Inquiring minds want to know. A final comma in the series would clear up the confusion.


No, this rule doesn’t have anything to do with Star Wars or Marvel fandoms. “FANBOYS” is a mnemonic device. It stands for For, And, Nor, But, Or, Yet, and So. These are the seven coordinating conjunctions. When joining two independent clauses with a coordinating conjunction, use a comma.

I played basketball, but I could never win a gold medal.

The trap door opened, and I fell to the ground.

That snake is creepy, so I don’t want to hold it.

Remember, the comma comes between two independent clauses. That means these two parts of the sentence could stand on their own. “I played basketball” and “I could never win a gold medal” could make sense as independent statements. The coordinating conjunction “but” along with the comma helps glue them together into one streamlined thought.

Be on the lookout for fake FANBOYS like “however,” “therefore,” and “moreover.” These conjunctions usually require a semicolon when they join two independent clauses.

Quotation Marks

Whether quoting the President of the United States or your next-door neighbor, commas and quotation marks can be confusing. The rule here is straightforward. In American English, commas go inside the quotation mark:

“Life is what happens when you’re busy making other plans,” said John Lennon.

The rule is slightly different in British English — put commas outside the quotation marks across the pond. And don’t forget to drive on the left side of the road.

Featured photo credit: fizkes/ iStock

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