Run-on Sentences and Comma Splices

Run-on sentences and comma splices are closely related errors. A run-on sentence occurs when multiple independent clauses lack punctuation or connections in a single sentence, while a comma splice occurs when a comma is used to separate two independent clauses. Both of these kinds of errors detract from the overall clarity of your writing because they create faulty sentences that contain more than one idea. 

Correcting these errors starts with identifying clauses within sentences, but it also relies on using conjunctions and/or punctuation that accurately reflect the relationship between the information you are presenting.

A comma splice occurs when two independent clauses (complete sentences) are joined with a comma, as in the following sentence: 

e.g., I am drinking a lot of coffee today (1), I was up too late last night (2). 

1. First independent clause

2. Second independent clause

While the ideas in the above sentence are somewhat connected in content, each clause is actually independent. It is a comma splice. 

There are a few ways to resolve comma splices when they occur. Using the above example, we can fix the error by: 

1. Replacing the comma with terminal punctuation

Because the clauses on either side of a comma splice are independent, the error can be fixed by replacing the comma with a period or a semicolon. 

• e.g., I am drinking a lot of coffee today. I was up too late last night.  
• e.g., I am drinking a lot of coffee today; I was up too late last night. 

In some cases, to provide the above solutions with stronger flow and connection, you can add a transition word or phrase (with a comma) to the second clause: e.g., She drank her tea too quickly; as a result, she burned the roof of her mouth.

2. Leaving the comma in but adding a coordinating conjunction

Commas can be used between two independent clauses when the clauses are joined by a coordinating conjunction:

• e.g., I am drinking a lot of coffee, for I was up too late last night. 

Use the acronym F.A.N.B.O.Y.S. to identify conjunctions that you can use to eliminate comma splice errors: F (for) A (and) N (nor) B (but) O (or) Y (yet) S (so).

Run-on sentences occur when two or more independent clauses are joined together without any punctuation or conjunction, as in the following sentence: 

e.g., The results were tabulated (1) they turned out to be statistically significant (2). 

1. First independent clause

2. Second independent clause

The strategies for resolving run-on sentences are generally the same as the ones for comma splices; for the above example, we can fix the error by: 

1. Inserting terminal punctuation (with or without a transition) between the two independent clauses 

• e.g., The results were tabulated; ultimately, they turned out to be statistically significant. 

2. Placing a comma and coordinating conjunction between the two independent clauses 

• e.g., The results were tabulated, and they turned out to be statistically significant.