Online Writing Lab

Comma Splices, Fused Sentences, and Run-Ons

Comma splices, run-ons, and fused sentences are all names that refer to compound sentences that aren’t punctuated properly.  (More on compound sentences) A comma splice occurs when a comma is used between two independent clauses.  (More on independent clauses) This creates a problem since a comma alone cannot be used to separate two independent clauses.  Unlike a comma splice, a run-on is two independent clauses merged together with no punctuation in between. (A fused sentence is another name for a run-on.)   Both comma splices and run-ons create grammatical problems.

Writers tend to create run-ons and comma splices when there are two sentences that are closely related to each other.  Because they are closely related, it can be hard to recognize that they are both separate independent clauses and need to be punctuated as such. 

The good news, however, is that while comma splices are quite common, they are easy to fix.  Comma splices can be fixed three different ways:

  1. Add a coordinating conjunction (for, and, nor, but, or, yet, so) after the comma.
  2. Change the comma to semicolon.
  3. Change the comma to a period.

The following passages are incorrect; the first contains one comma splice, and the second contains two comma splices:

Example #1

  • Our professor reviewed for the test in class, several of us went to the library afterwards to study. 

The comma between class and several is a comma splice since it is between two independent clauses.  A coordinating conjunction can be added to the comma to keep it as one sentence, or the two independent clauses can be separated into two separate sentences:

  • Our professor reviewed for the test in class, and several of us went to the library afterwards to study.
  • Our professor reviewed for the test in class; several of us went to the library afterwards tostudy.
  • Our professor reviewed for the test in class.  Several of us went to the library afterwards to study. 

Note:  Both of the last examples are grammatically correct since either a semicolon or a period can be used between two independent clauses, but the semicolon is particularly appropriate here since the first independent clause leads to the second.

Example #2

  • The coach was mad at his team, he told the players that they had to work harder in practice, he made them watch extra film to prepare for the next game. 

This passage contains two comma splices: between team and he and between practice and he.  As before, it can be corrected several different ways.  Here are a few examples:

  • The coach was mad at his team.  He told the players that they had to work harder in practice, and he made them watch extra film to prepare for the next game.
  • The coach seemed mad at his team, so he told his players that they had to work harder in practice.  He also made them watch extra film to prepare for the next game.

Correcting Comma Splices Exercises