Fragments and Run-Ons

Learning Objectives

  • Identify which punctuation to use when correcting run-on sentences and fragments

If you have issues with sentence construction, it’s usually a combination of comma splices, fragments, and run-ons. It’s less important that you know what those terms mean, than that you can actually fix the problem.

A proverb written on a piece of paper that says "Worry weighs a person down; an encouraging word cheers a person up. Proverbs 12:25".

Figure 1. Which sentence structure type is exhibited in the above Proverb? Is it “Sentence, conjunction sentence.”,”Sentence. Sentence.”, or “Sentence; sentence.”?

Here’s a simple way to think about it.

You can combine two sentences with a comma and a conjunction:

  • Sentence, conjunction sentence.
  • I love reading, and he loves writing.

You can also separate out your two sentences:

  • Sentence. Sentence.
  • I love reading. He loves writing.

You cannot combine two sentences with just a comma and no conjunction (that’s a comma splice):

  • Incorrect: Sentence, sentence
  • Incorrect: I love reading, he loves writing.

You could fix this sentence by adding in a conjunction like “and” or “but.” You can also fix this issue by using a semicolon. (A way to remember this is to think about the semicolon as working like a period.)

  • Sentence; sentence.
  • I love reading; he loves writing.

Using a semicolon to combine two complete sentences is an easy way to vary your sentence construction and avoid short choppy sentences. As long as you remember that your semicolon needs to connect two complete sentences, you will be set.

Try It


Let’s try some examples where you finish the sentence.

Guess what, there’s one more fun way to avoid the dreaded run-on or comma splice and make yourself look like a sophisticated, professional writer. Use a colon. It’s easy: A colon works just like a period. (See how we did that?)

  • Sentence: Sentence.
  • Sentence: anything (but not a full sentence).

The things you have to remember is that when you use a colon to combine two sentences, they need to be closely related (usually the second sentence is explaining something about the first sentence) and you need to capitalize the second sentence. Here’s are two examples:

  • I love eating out: McDonald’s is awesome.
  • Sentence: Sentence.
  • I love eating out: anything but McDonald’s.
  • Sentence: not a full sentence.

Try It

In summary, you have a variety of options for combining sentences and using appropriate punctuation to prevent fragments or run-ons:

  • Sentence. Sentence.
  • Sentence, conjunction sentence.
  • Sentence; sentence.
  • Sentence: Sentence.
  • Sentence: anything but a sentence.

Writing Workshop: Sentence types

Open your Working Document to the section titled “Sentence Types.”


STEP 1: Create a variety of sentences with this initial first sentence, using the different formats listed on the course page. After each example, explain, in your own words, why your answer makes sense.

For example, we’ll complete the first one for you.

  • Initial first sentence: Antonio wants to be a filmmaker.
  • Format: Sentence. Sentence. (Note the period)
  • Final product: Antonio wants to be a filmmaker. He hopes to make movies about the importance of the Black Lives Matter Movement.
  • Explanation: We have two complete sentences. Each can stand on its own as a sentence.


Now make your own:


  1. Sentence, conjunction sentence. (remember, conjunctions are those little words in fanboys – for, and, nor, but, or, yet, and so)Example:
  2. Sentence; sentence. (Note the semicolon)Example:
  3. Sentence: Sentence. (Note the colon and capital “S” for the second sentence.)Example:
  4. Sentence: anything but a sentence.  (Note the colon)Example:


STEP 2: Indicate all of the punctuation marks (semi-colon, period, colon, and/or comma) that could be used in the sentences and explain why.


For example,

  • My sister was always the smart one in our family __ it’s not surprising that she did well in school.
    • Semi-colon or colon would work because we have two complete sentences.
    • A period would not work because of the small i in it’s.
    • A comma would not work because you can’t put two sentences together with just a comma (comma splice).


  1. I truly dislike the first day of the semester ___  everyone is nervous.
  2. The school cafeteria is overpriced ___ but the food is fairly decent.
  3. My father has worked hard every day of his life ___ He inspires me to be successful in college.
  4. I could not believe the ridiculous prices at the school bookstore __ 20% more than Amazon.


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