Grammar Guide

Run-On Sentences

When two or more complete sentences are properly combined to form one sentence, the result is called a compound sentence. Run-on sentences occur when two or more complete sentences are combined to form one sentence, but without proper punctuation. A run-on sentence can be long or short. 

Example: I wasn’t sure how to ride a bike I was nervous. 

Although this sentence is short, it’s a run-on because there are two complete sentences—I wasn’t sure how to ride a bike and I was nervous—that are not separated with proper punctuation. Remember that complete sentences have a subject and a verb. 

There are a few different ways to fix run-on sentences. First, you can separate the two complete sentences with a period.

Example: I wasn’t sure how to ride a bike. I was nervous. 

Alternatively, you can use a semicolon to connect the sentences properly. 

Example: I wasn’t sure how to ride a bike; I was nervous.

You can also use a comma with a coordinating conjunction. A coordinating conjunction is a word that joins two of the same elements of a sentence, like two verbs, two nouns, two adjectives, or in this case, two complete sentences. There are 7 coordinating conjunctions: and, but, or, for, yet, nor, and so.

Example: I wasn’t sure how to ride a bike, and I was nervous. 

Be sure to use the coordinating conjunction that makes sense in the context of the sentence.

The last way to fix a run-on sentence is using a subordinating conjunction and a comma. Subordinating conjunctions have different functions, but in this case they’re used to show a cause-and-effect relationship between the two complete sentences being combined. Some common subordinating conjunctions are although, after, before, unless, as, because, even though, if, since, until, when, and while.

Example: Because I wasn’t sure how to ride a bike, I was nervous. 

Always use a coordinating or subordinating conjunction when using a comma to connect two complete sentences properly. When you separate a run-on sentence with a comma but don’t include a conjunction, the resulting error is called a comma splice. 

 

Practice:

1. Identify which of these are run-on sentences. 

1. She ran to catch the train that was coming into the station. 
2. Since I wanted to give my cousin a present I made sure to buy gift wrap. 
3. The computer wouldn’t turn on, which was very frustrating for the student who needed to finish their paper before the due date the next day. 
4. Lee couldn’t find the grocery list, so he wrote a new one. 
5. We needed to send the card in the mail we went to the post office. 

2. Fix the following run-on sentences using the listed method.

1. Period: 

My mom wanted a new car she bought an SUV yesterday. 

2. Semicolon: 

I walked into the kitchen I was looking for a snack. 

3. Coordinating conjunction and comma: 

He didn’t like studying in the quiet, empty library he went with his friends who wanted to study there. 

4. Subordinating conjunction and comma: 

Kitty was wandering the neighbourhood the family was not worried about their outdoor cat. 

 

Answers:

1. Run-ons:

1. Correct
2. Run-on
3. Correct
4. Correct
5. Run-on

2. Fixed sentences:

1. My mom wanted a new car. She bought an SUV yesterday. 
2. I walked into the kitchen; I was looking for a snack. 
3. He didn’t like studying in the quiet, empty library, but he went with his friends who wanted to study there. 

*Answers may vary if using a different coordinating conjunction

4. Although Kitty was wandering the neighbourhood, the family was not worried about their outdoor cat. 

*Answers may vary if using a different subordinating conjunction

 

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