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Identifying Run-On Sentences

Identifying Run-On Sentences

Author: Sophia Tutorial

Identify or correct run-on sentences.

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what's covered
This tutorial will cover run-on sentences, and how they can be corrected in writing. The specific areas of focus include:
  1. Review of Proper Sentence Components
  2. Identifying Run-On Sentences
    1. Comma Splices
    2. Conjunctions
  3. Correcting Run-On Sentences
  4. Avoiding Run-On Sentences

1. Review of Proper Sentence Components

Recall that a proper, correct sentence has at least three ingredients:

  • Subject
  • Verb
  • Full thought

A clause made up of just those three elements is called an independent clause.


We are going swimming.

See the subject and the verb? Also note that this is an entire thought all on its own, making it a full sentence.

A sentence can have more than one independent clause and still be grammatically correct:

Today is my birthday, so all my friends are coming for dinner.

You can see that there are two independent clauses here. Each has its own subject (highlighted in orange) and its own verb (highlighted in red) and makes up a complete thought. These two independent clauses could be two separate sentences.

But to show how these two thoughts are connected, a coordinating conjunction (highlighted in blue) is used to unite them into one sentence. Note that you have the first clause, then a comma and the coordinating conjunction, and then the second clause. That comma is essential with a compound sentence such as this.

2. Identifying Run-On Sentences

Now that you’ve got a handle on what makes a full sentence, you can start thinking about run-on sentences. A run-on sentence is a sentence that’s too full; it’s overflowing.

Technically, this means a run-on sentence is a sentence that includes multiple independent clauses that are not connected correctly. This will happen when there are multiple clauses that are connected without the use of correct punctuation or either coordinating or subordinating conjunctions.

In fact, those three tools (punctuation, coordinating conjunctions, and subordinating conjunctions) will be how you fix run-ons, and you’ll get to them in a bit. First, you need to learn how to spot the problem.

Run-on sentences really are a problem because they can be very confusing for your readers; they make your sentences unclear. Thus, you need to become an expert at tracking them down.

term to know
Run-On Sentence
A sentence that includes multiple independent clauses that are not connected correctly.

2a. Comma Splices

The first thing to look for is a comma splice. This is one of the most common causes of a run-on.

A comma splice is a grammatically incorrect sentence in which a comma separates two or more independent clauses.

Remember how the previous example had an independent clause plus a comma and a coordinating conjunction plus another independent clause? What if you took out that coordinating conjunction?

Today is my birthday, all my friends are coming for dinner.

Now you have two independent clauses, but instead of being united, think of that comma as a knife splicing them into two pieces. This is not grammatically correct in English because instead of bringing these two ideas together, that comma splice awkwardly separates them.

term to know
Comma Splice
A grammatically incorrect sentence in which a comma separates two or more independent clauses.

2b. Conjunctions

Now consider the following sentence.

All of my friends are coming to dinner and we are having cake.

Is this a run-on or not? To find out, there are some questions about this sentence that you can ask yourself.

step by step
  1. First, ask how many pairs of subjects and verbs there are. In this sentence, there are “friends” plus “are coming,” and “we” plus “are having.” That’s two.
  2. Next, you have to ask how many independent or dependent clauses there are. That first clause is an independent clause with a subject, a verb, and a full thought. Then in the second clause, you see “and we are having cake.” That’s a dependent clause.
  3. Finally, you need to check by asking what jobs the coordinating and/or subordinating conjunctions are performing. You can see there is the coordinating conjunction “and.” Is this coordinating conjunction doing its job? Here you see that, no, it’s not. You know this because it’s not paired with a comma. Therefore, you know that this is a run-on sentence.

3. Correcting Run-On Sentences

There are actually a few different ways to correct run-on sentences.

The first fix is to break apart the sentence into its independent clauses, each of which will transform into its own sentence, punctuated and capitalized correctly.

The dog slept on the bed. He was tired.

The second solution is to connect the two classes using a coordinating conjunction and a comma.

The dog slept on the bed, for he was tired.

The third correction is a semi-colon, which is a piece of punctuation specifically designed to connect two independent clauses into a sentence that isn’t a run-on.

The dog slept on the bed; he was tired.

Finally, you can remedy this error by adding in a subordinating conjunction.

The dog slept on the bed because he was tired.

Which method you choose will depend on what kind of run-on you’re dealing with, how you want each sentence in the paragraph to work together, and what your overall goal is for the sentence, paragraph, or paper. In short, correcting a run-on is about choosing the way you want your sentences to sound.

By practicing these methods, you can make an informed choice about how to change any sentence.

Below you can see how this might work in a paragraph.

I was done with breakfast I went to work. I said hi to everyone and they said hi back. I had a lot of work to do, and I was busy I like the work, so I was happy. At the end of the day, everything was completed I worked hard.

Clearly this paragraph has a lot of errors. Here’s how you might fix them:

In the first sentence, there are two independent clauses without proper connection. You can add in a coordinating conjunction and a comma to make these two sentences connect more clearly:

I was done with breakfast, so I went to work.

In the second sentence, there are two independent clauses united by a coordinating conjunction. But what’s missing? The comma:

I said hi to everyone, and they said hi back.

Now in the third sentence, there are two compound sentences incorrectly connected, which is pretty confusing. Add in a semi-colon to clear that sentence up:

I had a lot of work to do, and I was busy; I like the work, so I was happy.

In the last sentence, there is a prepositional phrase and then two independent clauses. Use a subordinating conjunction to make that second clause dependent:

At the end of the day, everything was completed because I worked hard.

Now you have a really good paragraph.

4. Avoiding Run-On Sentences

Now that you know how to fix these run-ons, you can also work on avoiding them altogether as you’re writing.

You know that in a typical sentence in English, it’s not necessary to include more than two clauses. Having multiple clauses doesn’t necessarily lead to a run-on, but it can.

In fact, it’s a lot easier to end up making the kind of grammatical error that leads to a run-on when you’re writing a sentence with lots of clauses. Thus, one way you can avoid run-ons is by keeping your sentences to two clauses or fewer.

Another way to avoid the run-on trap is to always think about how you started a sentence as you’re writing it. If you’re so far into a sentence that you can’t remember the way it began, you might just be churning out a run-on.

Therefore, if you find you’re writing a sentence that seems like it’s becoming a run-on, go ahead and cut it apart into two sentences.

You can do this by:

  • Finding the first independent clause, and letting it be its own sentence
  • Moving on to the next few clauses to see how those can be punctuated or written correctly as a sentence

You will end up with two complete and correct sentences instead of one ungainly run-on.

In this tutorial, you reviewed the components of a proper sentence and how independent and dependent clauses can be united into complete sentences. You then learned how to identify run-on sentences by looking at comma splices and improper usage of conjunctions.

Finally, you practiced some methods for correcting run-on sentences, as well as for avoiding run-on sentences completely as you’re writing.

Good luck!

Source: This work is adapted from Sophia author Martina Shabram.

Terms to Know
Comma Splice

A grammatically incorrect sentence in which a comma separates two or more independent clauses.

Run-On Sentence

A sentence that includes multiple independent clauses that are not connected correctly.