Commas: Misuse of Commas

Commas as a whole are useful; they are grammatical tools that allow you to keep your intended meaning clear. When you use them correctly, you guide your readers to understand your words in the right way, preserving your ideas with the right separations, or pauses. When commas are misused, whether it is overuse or under use, you run the risk of confusing, irritating and frustrating your readers because your sentences are chopped into too many pieces. In some cases, you are unintentionally misinforming readers as well.

As was mentioned in the introduction to this series of guides, overuse of commas is one of the most common grammatical mistakes. Using too many commas results in stilted, disjointed sentences that are difficult, if not impossible, to read. Avoid the following common mistakes in comma usage, and your words are sure to make more sense to those who read them.

Using a comma in front of “that”

In most cases, a comma preceding a clause including “that” is incorrect. However, if you are like many writers, you might find yourself inclined to include one. Do not. Avoid making this common mistake because “that” is usually used to introduce an essential, or restrictive, clause, making the clause necessary for the sentence to retain its meaning. For example:

INCORRECT: The colors, that were used to decorate the reception hall, were well-matched.

CORRECT: The dress that she wore to the wedding was beautiful.

Separating correlated pairs

When the second part of the sentence pairs with the information in the first part through correlation, a comma is not used. For example:

INCORRECT: The article is a not only a masterpiece of the written word, but is grammatically sound.

CORRECT: Her new car was sporty looking and creates a distinguished look.

Separating a verb from its subject

Never separate a subject from its verb; this creates a disjointed sentence with an unnecessary pause and is grammatically incorrect as well. Below, “is” is the verb, and its subject is “one of the smartest things.”

INCORRECT: One of the smartest things a writer can do, is learn how to use commas correctly.

CORRECT: One of the smartest things a writer can do is learn how to use commas correctly.

Separating verbs

Sometimes verbs are used in multiple locations in a sentence. When this occurs, you should not separate them with a comma. Both “jogged” and “walked” are verbs that apply to the subject of “she” in the following sentences.

INCORRECT: She jogged for 30 minutes, and walked for 20 minutes.

CORRECT: She jogged for 30 minutes and walked for 20 minutes.

Offsetting a dependent clause

When one of the clauses in a sentence is dependent on the other and appears at the end of the sentence, the dependent clause is not offset by a comma.

INCORRECT: Sylvia went to the store, because she needed eggs.

CORRECT: Her performance exceeded her expectations because she put in extra preparation.

The comma splice and run-on sentences

Comma splices and run-on sentences are two of the most common comma errors. Comma splices are using a comma to connect two independent clauses with no coordinating conjunction. Run-on sentences are created when you combine two independent clauses without the comma. While these are both common mistakes, they create hard-to-read sentences, where the meaning is often unclear or the right ideas, thoughts or actions are not clearly separated or connected. Both comma splices and run-on sentences are addressed in more detail in their own respective sections of’s writing resources, so check them out for more help with avoiding these common errors.

How to avoid comma misuse

While all the comma rules presented in this series of guides may seem confusing, it is important to avoid breaking them, whether you tend to overuse or under use commas. The best ways to master commas is through learning the individual rules as you go and through reading what you write out loud, inserting pauses in the words you speak to replace the commas. If you cannot imagine using the pause at a location within a sentence to provide clarity, omit the comma. If the sentence is confusing or a pause seems natural, include the comma. As you gain knowledge, practice applying rules and proofread your work thoroughly, the mastering of comma usage comes naturally.