A run-on sentence is a sentence where two or more independent clauses have been incorrectly joined together. An independent clause contains both a subject and a verb and can stand on its own as a complete sentence. Some examples of independent clauses include “Jane ate dinner,” “John went to the store,” and “Sue made a pie.”
A comma splice is a grammatical error where a run-on sentence uses a simple comma to separate independent clauses. Here’s an example: “Jane ate dinner, John went to the store.” There are a few different ways to fix a run-on sentence that has a comma splice. One way is to change the commas into periods, and break the line into multiple independent sentences. For short sentences, this is often an easy solution, as in “Jane ate dinner. John went to the store.” Another method of fixing comma splices is changing the commas to semicolons. This could make a long sentence more difficult to read, but for simple, closely related sentences this method works well. Here is an example of semicolons used to fix a run-on sentence: “Jane ate dinner; John went to the store.”
You can also fix the problem by adding one of the following coordinating conjunctions to the sentence: and, but, or, nor, for, or so. Coordinating conjunctions should appear before the final independent clause in a series. Only one is required, even if you have multiple independent clauses in a row. A two-clause sentence with a comma and a coordinating conjunction looks like this: “Jane ate dinner, and John went to the store.” A three-clause sentence with a comma and a coordinating conjunction looks like this: “Jane ate dinner, John went to the store, and Sue made a pie.”
Turning one of the independent clauses into a subordinating clause (a clause that can’t stand on its own as a sentence) is an even more sophisticated way to repair a run-on sentence. When repaired this way, the example from above looks like this: “While Jane ate dinner, John went to the store.” While Jane ate dinner is a subordinating clause here because it doesn’t make sense as a sentence on its own.
Run-on sentences that don’t contain any punctuation at all between the independent clauses are called fused sentences. An example of a fused sentence is “Jane ate dinner John went to the store.” Any of the methods used to fix comma splices can also be used to fix fused sentences.