Run-on sentences are sentences that contain too many ideas without proper punctuation. Not all long sentences are run-on sentences. It is perfectly acceptable to join several related ideas in one compound sentence. However, if you don't follow punctuation and syntax rules, a sentence can become a run-on. A simple explanation of run-ons and some run-on sentences examples should clarify this point.
Components of a Sentence
Each sentence has three necessary components:
Subject: What is this sentence about? The subject is usually, but not always, a noun or a pronoun.
Action: What is the subject of the sentence doing? The action is always a verb.
Complete thought: What is the purpose of this sentence?
For more on sentence structure, explore our examples of syntax.
Simple Example Sentence
Let's look at how a simple sentence -- like "Jim is cold" -- incorporates subject, action and complete thought. In this sentence:
There is a subject: Jim.
There is an action: "Is," which is a form of the verb "to be." In this case, Jim is doing the action of "being cold."
There is a complete thought: The purpose of this sentence is to tell the reader that Jim is cold.
Sentences with these three components are called independent clauses. Independent clauses can stand on their own - they form their own sentences. If a sentence is lacking in one of the three components, it is called a dependent clause. Dependent clauses can't stand alone; they need to be joined to another clause.
For more help differentiating between the two, try our article comparing independent and dependent clauses.
Defining a Run-on Sentence
Independent and dependent clauses can be joined together to create compound sentences. A run-on sentence has two or more clauses which are joined improperly. To avoid run-on sentences, compound sentences come with rules:
Two related independent clauses can be joined using a semicolon. "Jim is cold; he wants to go inside." Both "Jim is cold" and "he wants to go inside" could be standalone sentences. To convey further information, however, they've been joined with a semicolon. This a correct compound sentence.
An independent clause can be made dependent on another clause by using a coordinating conjunction. For example: "Jim is cold, but he wants to stay outside." The second clause, "He wants to stay outside," could be an independent clause. However, the coordinating conjunction "but" makes it dependent on the first clause.
Types of Run-on Sentences
Run-on sentences come in many different varieties. Here are three of the most common types:
A comma splice happens when a comma, rather than a semicolon, has been used to join independent clauses.
A fused sentence mashes two main clauses together with no punctuation at all.
Polysyndeton refers to the use of more conjunctions than a sentence requires.
Fixing Run-on Sentences
Here follow examples of each type of run-on sentence described above, with explanations for how to fix them.
Comma Splice Example
Kelly likes to cook, she makes chicken every day.
This is a classic comma splice. "Kelly likes to cook" is an independent clause that can stand by itself. "She makes chicken every day" is also an independent clause that could stand by itself. Joining these two clauses calls for a semicolon, not a comma:
Kelly likes to cook; she makes chicken every day.
Fused Sentence Example
Mary likes dogs she has a beagle.
This exemplifies a fused sentence: two independent clauses written together without any punctuation or conjunction to separate them. All that's necessary to fix this sentence is to insert the proper punctuation. Both of the following are valid ways of rewriting the same sentence.
Mary likes dogs; she has a beagle.
Mary likes dogs. She has a beagle.
We went to the park and we ate dinner and we got ice cream and when it got dark we chased fireflies.
This is polysyndeton: the use of excessive conjunctions to extend the length of the sentence. In this case, the word "and" is overused. Sometimes, the overuse of conjunctions like "and" is a deliberate rhetorical choice. Most of the time, however, it's a simple error with an even simpler fix: divide the statement into separate sentences with a bit of punctuation:
We went to the park. Then, we ate dinner and got ice cream. When it got dark, we chased fireflies.
Don't Run On
Run-on sentences are easy mistakes. Run-on sentences appear in all sorts of writing, especially in first drafts and time-sensitive writing. As long as you keep to the advice above, however, you should be golden.
If you'd like to read more about the most common kind of run-on sentence, have a look at these examples of comma splices. Happy editing!