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Grammar: Run-On Sentences and Sentence Fragments

Run-On Sentences

A run-on sentence occurs when two or more independent clauses (also known as complete sentences) are connected improperly.

Example: I love to write papers I would write one every day if I had the time.

There are two complete sentences in the above example:

Sentence 1: I love to write papers.
 
Sentence 2: I would write one every day if I had the time.

 


One common type of run-on sentence is a comma splice. A comma splice occurs when two independent clauses are joined with just a comma.

Example of a comma splice: Participants could leave the study at any time, they needed to indicate their preference.
Sentence 1: Participants could leave the study at any time.
 
Sentence 2: They needed to indicate their preference.

 

Some comma splices occur when a writer attempts to use a transitional expression in the middle of a sentence.

Example of a comma splice: The results of the study were inconclusive, therefore more research needs to be done on the topic.
Sentence 1: The results of the study were inconclusive
 
Transitional expression (conjunctive adverb): therefore
 
Sentence 2: More research needs to be done on the topic

To fix this type of comma splice, use a semicolon before the transitional expression and add a comma after it. See more examples of this on the semicolon page.

Revision: The results of the study were inconclusive; therefore, more research needs to be done on the topic.

You can correct a run-on sentence by connecting or separating its parts correctly. There are several easy ways to connect independent clauses.

Correcting Run-On Sentences

A run-on sentence can be fixed by connecting its parts correctly. There are several ways to connect independent clauses.

  1. Use a period. The easiest way to fix a run-on is to split the sentence into smaller sentences using a period. This revision works especially well with longer sentences. Check, however, to make sure that this solution does not result in short, choppy sentences.
    Revision example: I love to write papers. I would write one every day if I had the time.
  2. Use a semicolon. Inserting a semicolon between independent clauses creates a grammatically correct sentence. Using a semicolon is a stylistic choice that establishes a close relationship between the two sentences.
    Revision example: I love to write papers; I would write one every day if I had the time.
  3. Use a comma and a coordinating conjunction. A comma, paired with a coordinating conjunction (such as and, but, or or), corrects a run-on sentence. This method emphasizes the relationship between the two clauses.
    Revision example: I love to write papers, and I would write one every day if I had the time.
  4. Use a subordinating conjunction. Turn one of the independent clauses into a dependent clause. A subordinating conjunction (such as because, unless, and although) connects two clauses to create a complex sentence. This option works to cement the relationship between the two parts of the sentence and may improve the flow of the clauses.
    Example: Because I love to write papers, I would write one every day if I had the time.

However you decide to revise for run-on sentences, remember that maintaining sentence variety helps to keep the writing clear and interesting for your readers.

Sentence Fragments

A sentence fragment is a string of words that does not form a complete sentence; there is a  necessary component of a complete sentence missing. This missing component may be a subject (usually a noun) or a predicate (verb or verb phrase) and/or when the sentence does not express a complete idea.

Here is an example of a fragment with a missing subject.

Example of a fragment: Shows no improvement in any of the vital signs.

The sentence above is a fragment since there is no subject (Who shows no improvement?). Fragments can be corrected by identifying the missing element and including it.

Revision: The patient shows no improvement in any of the vital signs.

Here is an example of a fragment with a missing predicate, or action:

Example of a fragment: The doctors, who were using peer-reviewed research articles that contributed to the body of knowledge in their fields, which was obstetrics.

Notice here that although the sentence is quite long, it still contains no action (What are the doctors doing?). Once identified, the sentence can be corrected easily.

Revision: The doctors, who were using peer-reviewed research articles that contributed to the body of knowledge in their field, improved their knowledge of obstetrics.

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Knowledge Check: Run-On Sentences and Sentence Fragments