Comma Splices, Run-On Sentences, & Fragments

Hear the Lecture

Punctuation Errors

I've noticed over the years that three aspects of punctuation are confusing for many ESL/EFL teachers.  These involve punctuation errors that are often considered important in the context of freshman composition courses--but really have wider implications for ESL/EFL students who need to be accurate writers. Thus, understanding comma splices, run-on sentences, and fragments is important for those of us who teach ESL/EFL to students who are likely do degree studies in a U.S. college or university. 

I'm going to give brief definitions and examples in this section of the lecture.  In addition, I will provide links to web-based activities that give you more information about these topics. 

Comma Splice Defined

A comma splice is the mis-use of a comma to make a compound sentence.  A compound sentence is made of two or more simple sentences that are combined to make a new sentence.  The new compound sentence should be created with particular types of connections. 

To make a compound sentence, you either

1. combine the two simple sentences by using a comma and one of the coordinating conjunctions

He loves sociology, and he plans to major in that disciplinary area.
2. combine the two simple sentences by using a semicolon
He loves sociology; he plans to major in that disciplinary area.
A comma splice makes the connection but leaves out the coordinating conjunction:
*He loves sociology, he plans to major in that disciplinary area.
That's it.  Splice means to "combine."  We splice rope--or audiotape--or videotape.  And we splice commas--or better, we splice sentences using commas.  But we aren't supposed to.  A comma splice is a compound sentence with a comma but without a coordinating conjunction.

A common mistake by native speakers as well as ESL/EFL writers is to think that a conjunct (linking word, logical connector, conjunctive adverb) can be used with a comma to tie a sentence together.  Such a combination creates a comma splice because the adverb cannot take the place of a coordinating conjunction.

*He loves sociology, however, he plans to major in business administration.
By the way, this mistake is very much an American issue.  Punctuation is approached in the States on a rule-based basis as fits our society.  Rules rather than traditions are the basis for the explanations that we find in U.S. grammar books in the sections on punctuation.  You will definitely find more commas splices in materials published in the U.K. and Australia than in the U.S.
Examples of Comma Splices from Student Writing

1. *An educated person needs to know about many things other than the skills needed for a job, thus, college students should be required to take courses that are not specifically related to their careers.

2. *People are sometimes judged by their outward appearance, however, their inner personalities are much more important.

Remembering the Coordinating Conjunctions

The purpose of the FANBOYS mnemonic device is to help teachers and students remember the coordinating conjunctions.  There are just seven of them--definitely a closed class.  The most important of these are the words and, or, and but.  The others have more limited use. 

F for
A and
N nor
B but
O or
Y yet
S so

Run-On Sentences

Now let's take a look at the punctuation error that is called a run-on sentence.  Years ago, I heard an ESL teacher explain run-on sentences to her class.  She had mistakenly thought that run-on was the same as "to talk too much"--to "run-on at the mouth" in the rather unpleasant expression.  While I know that some writers do go on and on and on that's not the point of run-on sentence. 

Run-on Sentence Defined

A run-on sentence is a compound sentence that has been incorrectly punctuated.  There are two types of run-on sentences:

1.  One type involves writing that has sentence after sentence presented without end punctuation--without a period at the end of one sentence or a capital letter at the beginning of the next.  Sentences just run together. This type of writing tends to be the product of a new writer who hasn't yet learned to separate speaking from writing.

He loves sociology as a discipline however he plans to major in anthropology to the dismay of his mother she prefers geography.
2. Remember that the comma splice uses a comma to tie a sentence together--without a coordinating conjunction.  This type of  run-on sentence does the opposite by using the coordinating conjunction but leaving out the comma.
He loves sociology and he plans to major in that disciplinary area.
Examples of Run-On Sentences

1. Economics 111 is very demanding it requires homework every day, quizzes each Friday, and gives major tests.

2. Economics 111 is very demanding and many students avoid taking it.


While comma splices can seem like something that only we English majors can get very excited about, run-on sentences and sentence fragments are more important areas for all writing teachers to learn about and to find ways to help students move beyond.  Both run-on sentences (of the first type) and sentence fragments generally indicate that a student has not yet progressed to an advanced level as a writer of English prose.  Thus, they can sometimes be developmental stages that learners go through.  Of course, sometimes they are just signs of writers in a hurry who haven't taken the time to edit their products carefully enough.  Let's take a look at a definition and some examples of fragment and then look at a sample of student writing that shows the results of fragments for readers.

Sentence Fragment Defined

A fragment is a piece of a sentence used as if it were a complete sentence.  Look at the following example to see a typical fragment:

He loves sociology.  Because he is fascinated with understanding how people behave in social groups.
The 2nd part of this examples is an adverbial clause that is presented as a complete sentence.  That's a very common source of fragments.  We often talk this way--putting a pause between the main sentence and the clause that gives the reason for something.  But we need to learn that we don't write this way in formal written English. 

There are times when fragments are "legal."  We use them in headings, for example, and in lists.  And we sometimes use them in formal written English when we mimic the question-answer style of conversational English.  Look at this sample from the newspaper in Fort Collins, Colorado.  Here the writer asks a question and then answers it with words rather than complete sentences.  (The answer, by the way, turns out to be house cats.)

from “City’s Leash Ordinance Is Doing Wildlife a Favor”

What predator do you think kills the most livestock in this country after the coyote?

Black bear?  Mountain lion?  Bobcat?  Fox?  Eagle?

No, think closer to home.

In sum, when fragments are used deliberately by a writer for some dramatic effect--that's ok.  We are looking for fragments created by less experienced writers who still are not fully in command of English written sentence structures.  Look at the following sample of student writing to see how fragments look in real authentic student produced English.


Fragments in a Sample of Student Writing

As you can see from what she says about herself, the writer is an international student who is native speaker of English.  Native speakers and NNS speakers can have trouble with learning to separate talking from writing.  You will see similar patterns in the writing of ESL/EFL students, especially those who have better spoken English than written English.  I suggest that you copy this sample (highlight it, copy it, and then paste it into your word processing system) and look through to find the various fragments.  Often they are adverbial clauses that have been punctuated as independent sentences rather than attached to the independent clause to which they are related.

How Money Would change My Life
(A Student Writing Sample)

     If I won one million dollars, it would change my life in many ways.  Once I had actually received the money, I would make donations to charitable causes.  When I compare the opportunities in North America with those for people in the third world.  It is difficult to imagine how we survived.  If I should win one million dollars, I would use some to build schools.  I would also donate money for uniforms, books, and meals.  Remembering back then that many of my classmates were unable to attend school because they were lacking such items.  My next project would be to build or maintain existing health clinics.  Be sure that they are well staffed and equiped with modern equipment necessary to sustain and improve lives.  So often babies are dying because they are not immunized.  Because there are no available or nearby facilities to provide health care.  It would change my life to give an education to a brilliant child.  Who would otherwise end up washing clothes at the riverside for pennies a day.  Give life to a child who otherwise would have died.  Because there were no facilities nearby for treatment.  These things would bring satisfaction to me and change my life.  If I could change the lives of a few other people.

Please send me your questions and comments at  Thanks.