Rhetoric and Composition/Run-on sentence

What is a run-on sentence?

While a run-on sentence, also known as a fused sentence, might just seem to be the type of sentence that goes on and on without a clear point, the technical grammatical definition of a run-on sentence is one that fuses, or "runs together," two or more independent clauses (basically, clauses that express a complete thought and could stand on their own as full sentences) without punctuation to separate them. They may have nothing between them, or they may have a coordinating conjunction (and, or, nor, but, for, so yet) between them but not the comma that needs to accompany the coordinating conjunction when separating two independent clauses.

You can often find run-on sentences in your work by reading it aloud. The run-on sentences will trip you up: you'll want to pause or otherwise come to some sort of end when you hit the end of an independent clause, but a run-on, with its lack of punctuation, doesn't signal you to do that. Try reading the following examples of run-on sentences out loud, and notice where two clauses seem to collide:

Examples of run-on sentences

• Every day, millions of children go to daycare with millions of other kids there is no guarantee that none of them are harboring infectious conditions.
• Many daycare centers have strict rules about sick children needing to stay away until they are no longer infectious but enforcing those rules can be very difficult.
• Daycare providers often undergo extreme pressure to accept a sick child "just this once" the parent has no other care options and cannot miss work.

Fixing run-on sentences

Once you find a run-on sentence and notice where the two independent clauses "collide," you can then decide on how best to separate the clauses:

• You can make two complete sentences by inserting a period; this is the strongest level of separation.
• You can use a semicolon between the two clauses if they are of equal importance, and you want your reader to consider the points together.
• You can use a semicolon with a transition word to indicate a specific relation between the two clauses.
• You can use a coordinating conjunction and a comma, also to indicate a relationship.
• Or, you can add a word to one clause to make it dependent.

Examples of fixed run-on sentences

Notice how the sentences above have been punctuated in the following examples.

• Every day, millions of children go to daycare with millions of other kids. There is no guarantee that none of them are harboring infectious conditions.
• Many daycare centers have strict rules about sick children needing to stay away until they are no longer infectious; however, enforcing those rules can be very difficult.
• Many daycare centers have strict rules about sick children needing to stay away until they are no longer infectious, but enforcing those rules can be very difficult.
• Daycare providers often undergo extreme pressure to accept a sick child "just this once" because the parent has no other care options and cannot miss work.

Learn more under "commas with two independent clauses" here.