Grammar & Mechanics

Run-on sentences incorrectly join two or more independent clauses in a single sentence. Run-on sentences are similar to comma splices (review the Comma Splices handout for more information).  

Independent clauses contain a subject and verb. These clauses can function as complete sentences or can be joined in one sentence with the correct punctuation. The following example shows a run-on sentence with two independent clauses: 

The professor assigned a paper I wrote it after class. 

With no punctuation, the independent clauses “run into” each other and form a run-on sentence. To fix this error, choose one of these options:

Use a period or semicolon.  

• The professor assigned a paper. I wrote it after class. (The period separates the two independent clauses) 

• The professor assigned a paper; I wrote it after class. (The semicolon can join two independent clauses in the same sentence. A semicolon is a good option when linking two shorter independent clauses to avoid choppy sentences.) 

Use a comma and conjunction. 

• Conjunctions are connector words, such as for, and, nor, but, or, yet, so. 

• The professor assigned a paper, and I wrote it after class. (Using “, and” allows the writer to link two independent clauses.) 

Restructure the sentence. 

• I wrote a paper right after the professor assigned it. (The sentence is rewritten to avoid a run-on) 

Source consulted: Upswing Writing Lab 

Guide created by: C. Jones 3/4/2021  

Revised by: B. McCoid 1/19/2024

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