The Comma Splice

The comma (,) is one of the most often used punctuation marks, but using it correctly can be challenging. Where you use a comma can change the entire meaning of a sentence. In a series of guides, we will review a few of the most common mistakes with comma usage. Each grammar guide will provide helpful tips and tricks for finding and avoiding these mistakes when preparing your manuscripts. You can download each grammar guide as a PDF via the link at the end of the page.

THE COMMA SPLICE

Linking two independent statements with a comma is called a “comma splice”. An independent statement is a phrase that can stand alone as a complete sentence.

Everyday problem sentence:

He went to school, he learned nothing.

The phrases on either side of the comma are both complete sentences:

He went to school.

He learned nothing.

Scientific problem sentence:

Multiple genetic subtypes of progeria diseases have been identified in humans, some important manifestations of these diseases, such as skin cancer, are related to specific subtypes.

This problem sentence also consists of two independent (but more complicated) statements.

Multiple genetic subtypes of progeria diseases have been identified in humans.

Some important manifestations of these diseases, such as skin cancer, are related to specific subtypes.

The solution

When the independent statements are short, like in the first example problem sentence, we tend to want to join them together for readability. This approach can improve your writing, but it must be done correctly.

To decide if you have a comma splice, ask yourself the following questions:

  1. Does my sentence contain two independent statements that don’t need to stay together in one sentence for the reader to understand the meaning?

  1. Are the statements on each side of the comma complete sentences on their own?

If the answer to either of these questions is YES, then you can make each independent thought its own sentence, or you can add the word and after the comma. Adding the word and is especially helpful for making the first problem sentence sound good – this longer sentence is more readable than the two shorter sentences.

He went to school, and he learned nothing.

For the scientific example, either option is acceptable – the best option mostly depends on the preference of the author.

Option 1:

Multiple genetic subtypes of progeria diseases have been identified in humans, and some important manifestations of these diseases, such as skin cancer, are related to specific subtypes.

Option 2:

Multiple genetic subtypes of progeria diseases have been identified in humans. Some important manifestations of these diseases, such as skin cancer, are related to specific subtypes.

Using commas properly is an ongoing challenge, even for native English speakers. While there are many rules for their use, sometimes these rules are quite flexible and can be broken to ensure maximize readability and clarity.

Download the PDF for this grammar guide to keep these helpful tips for future reference.

“IMG_0831” by Ray Dehler is used under a Creative Commons Attribution 2.0 Generic (CC BY 2.0) License. The image was cropped.