Introduction to Academic Writing

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Grammar: Run-On Sentences


Run-on Sentences

Isabelle’s e-mail opens with two fragments and two run-on sentences containing comma splices. The e-mail ends with another fragment. What effect would this e-mail have on Mr. Blankenship or other readers? Mr. Blankenship or other readers may not think highly of Isaebelle’s communication skills or—worse—may not understand the message at all! Communications written in precise, complete sentences are not only more professional but also easier to understand. Before you hit the “send” button, read your e-mail carefully to make sure that the sentences are complete, are not run together, and are correctly punctuated.


Sentences with two or more independent clauses that have been incorrectly combined are known as run-on sentences. A run-on sentence may be either a fused sentence or a comma splice.

Fused sentence: A family of foxes lived under our shed young foxes played all over the yard.

Comma splice: We looked outside, the kids were hopping on the trampoline.

When two complete sentences are combined into one without any punctuation, the result is a fused sentence. When two complete sentences are joined by a comma, the result is a comma splice. Both errors can easily be fixed.


One way to correct run-on sentences is to correct the punctuation. For example, adding a period will correct the run-on by creating two separate sentences.

Using a semicolon between the two complete sentences will also correct the error. A semicolon allows you to keep the two closely related ideas together in one sentence. When you punctuate with a semicolon, make sure that both parts of the sentence are independent clauses.

Run-on: The accident closed both lanes of traffic we waited an hour for the wreckage to be cleared.

Complete sentence: The accident closed both lanes of traffic; we waited an hour for the wreckage to be cleared.

When you use a semicolon to separate two independent clauses, you may wish to add a transition word to show the connection between the two thoughts. After the semicolon, add the transition word and follow it with a comma. For more information on transition words, see Chapter 8 “The Writing Process: How Do I Begin?”.

Run-on: The project was put on hold we didn’t have time to slow down, so we kept working.

Complete sentence: The project was put on hold; however, we didn’t have time to slow down, so we kept working.

Coordinating Conjunctions

You can also fix run-on sentences by adding a comma and a coordinating conjunction. A coordinating conjunction acts as a link between two independent clauses.


These are the seven coordinating conjunctions that you can use: for, and, nor, but, or, yet, and so. Use these words appropriately when you want to link the two independent clauses. The acronymFANBOYS will help you remember this group of coordinating conjunctions.

Run-on: The new printer was installed, no one knew how to use it.

Complete sentence: The new printer was installed, but no one knew how to use it.

Dependent Words

Adding dependent words is another way to link independent clauses. Like the coordinating conjunctions, dependent words show a relationship between two independent clauses.

Run-on: We took the elevator, the others still got there before us.

Complete sentence: Although we took the elevator, the others got there before us.

Run-on: Cobwebs covered the furniture, the room hadn’t been used in years.

Complete sentence: Cobwebs covered the furniture because the room hadn’t been used in years.

KEY TAKEAWAYS for fragments and run-ons:

  • A sentence is complete when it contains both a subject and verb. A complete sentence makes sense on its own.
  • Every sentence must have a subject, which usually appears at the beginning of the sentence. A subject may be a noun (a person, place, or thing) or a pronoun.
  • A compound subject contains more than one noun.
  • A prepositional phrase describes, or modifies, another word in the sentence but cannot be the subject of a sentence.
  • A verb is often an action word that indicates what the subject is doing. Verbs may be action verbs, linking verbs, or helping verbs.
  • Variety in sentence structure and length improves writing by making it more interesting and more complex.
  • Focusing on the six basic sentence patterns will enhance your writing.
  • Fragments and run-on sentences are two common errors in sentence construction.
  • Fragments can be corrected by adding a missing subject or verb. Fragments that begin with a preposition or a dependent word can be corrected by combining the fragment with another sentence.
  • Run-on sentences can be corrected by adding appropriate punctuation or adding a coordinating conjunction.

The above lesson is adapted from: Successful Writing If you would like more help on run-on sentences, please review this chapter from Writers’ Handbook. Alternatively have a look at this quick lesson on run-on sentences from the OWL.


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