Comma Mistakes You Might Be Making

Hello and welcome to Maddie’s Grammar Lessons™ , Volume III. (I’m fun, I swear!)

A little background: I’m The Everygirl’s copy editor (and an editorial assistant), which entails editing stories from our writers for style and grammar. Through this, I’ve found that most people make the same mistakes — whether they’re seasoned writers or not.

So far, I’ve talked about the most common writing mistakes I see and common words and phrases that people misuse, so now I’m ready to dive into the king of punctuation: the comma. (Still fun! I’m listening to Candy Shop as I write this!)

Commas have the power to make a sentence clear and readable, or cause it to make no sense at all. Some people overuse them, some people underuse them, but these mistakes happen all of the time. Keep these in your back pocket for the next time you have to send a follow-up email or have to write an email to the Big Boss.


Comma splices

A comma splice is when you use a comma to join two independent clauses (clauses that can stand on their own and make sense as a full sentence — they are complete thoughts.) These aren’t necessary and shouldn’t be used.


I might not go to work tomorrow, I feel really sick.

I went for a run, I slipped and fell.

How to fix it:

Instead of using a comma, you can add a conjunction, make two separate sentences, or turn the comma to a semicolon.


I might not come to work tomorrow because I feel really sick. 

I went for a run; I slipped and fell.


Run-on sentences (missing commas)

A run-on sentence is formed when two independent clauses are joined together without a word to connect them or punctuation to separate them. They need to be joined by a comma or semicolon, or separated by a period.


I’m sorry I love you

I went to Starbucks I got an iced americano.


I’m sorry, I love you.

I went to Starbucks, and I got an iced americano.


Missing commas (AKA not using a comma between two independent clauses that are connected by a coordinating conjunction)

Don’t tune out yet, I know this is a lot of grammar jargon, but it isn’t nearly as complicated as it sounds. Independent clauses are clauses that can stand alone (see above); a coordinating conjunction joins two of them (and, but, or, etc.).


I went to Trader Joes, but I forgot to buy bananas.

(“I went to Trader Joes” and “I forgot to buy bananas” both can stand alone (independent clauses) and are joined by “but” (a coordinating conjunction.)


I went to Trader Joes but I forgot to buy bananas.

(Add a comma before the conjunction.)


Unnecessary commas

I have a theory that every human being on earth tends to either underuse or overuse commas (I’ve always leaned toward the latter). Some examples of overuse:


You can do it, too.


You can do it too.


You either love commas, or you don’t.


You either love commas or you don’t.


  • Maddy M Lefever

    I love all of the grammar posts! So helpful. Just wondering…Are you by chance an Enneagram Type 1? Lol

  • Annie C

    The funny thing about this article is that there’s a spelling error: in parentheses, you wrote “(Still fun! I’m listening to Candy Shop as a write this!),” but you mistakenly typed “a” instead of “I.”

  • lindsey

    Aren’t “I’m sorry” and “I love you” two independent clauses? “I’m sorry, I love you” would be a comma splice then, right?

  • MA

    Actually, technically, “I’m sorry I love you” and “You either love commas or you don’t.” are both actually situations where there are two separate independent clauses, thereby meaning that they technically require a comma AND a coordinating conjunction to join them or just a semi-colon.

    I’m sorry; I love you.

    You either love commas, or you don’t.

    Also, there is a third correct way to join two independent clauses: a semi-colon followed by a conjunctive adverb followed by a comma.
    For example:

    I enjoyed the party; however, he didn’t.

    A conjunctive adverb is an adverb like “however” or “nevertheless” that joins in a way similar to a conjunction.

    Final comment: People also often neglect to place commas after adverbs and prepositional phrases at the beginning of sentences (which denote that those words are actually part of the predicate and belong at the end of the clause). For example:

    Incorrect: At the school we learned about commas.

    Correct: At the school, we learned about commas.

    The author means, “We learned about commas at school”.

    (At the school) is a prepositional phrase acting as an adverb that is telling WHERE the action “learned” is happening. Ergo, it modifies the simple predicate, belongs to the complete predicate, and should be followed by a comma to emphasize that it belongs with the end of the sentence. This same principle holds true for adverbs at the beginning of sentences as well.

    Incorrect: Finally I finished the test.

    Correct: Finally, I finished the test.

    The author means, “I finished the test finally” or “I finally finished the test”.

  • Amy A

    I’m finding a lot of newly published books are using commas incorrectly; instead of using a semicolon to join two independent clauses, a comma is being used instead What’s written actually then becomes a run-on sentence. It can’t be a matter of spacing, as a comma takes up as much room as a semicolon. Is it lazy editing? I’d love to hear a book editor’s explanation of this new trend. As a proud grammar nerd, I’m focusing more on this inaccuracy than the actual book’s content, and it’s kind of annoying.

  • Vaida Jėčienė

    I’m sorry I love you
    I’m sorry, I love you.

    I’m pretty sure both of these are valid, they just convey different meaning.