Recall that a proper, correct sentence has at least three ingredients:
EXAMPLEWe are going swimming.
See the subject ("we") and the verb ("are going")? 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:
EXAMPLEToday is my birthday, so all my friends are coming for dinner.
You can see that there are two independent clauses here: "Today is my birthday" and "all my friends are coming for dinner." Each has its own subject and its own verb, 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 ("so") 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.
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 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.
And run-on sentences really are a problem, because they can be very confusing for your readers; they make your writing unclear. Thus, you need to become an expert at tracking them down.
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?
EXAMPLEToday 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.
An incorrect use of conjunctions or lack of proper punctuation can also lead to run-on sentences.
EXAMPLEAll of my friends are coming to dinner and we are having cake.
Is this sentence a run-on or not? To find out, there are some questions about this sentence that you can ask yourself.
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.
EXAMPLEThe dog slept on the bed. He was tired.
The second solution is to connect the two clauses using a coordinating conjunction and a comma.
EXAMPLEThe dog slept on the bed, for he was tired.
The third correction is a semicolon, which is a piece of punctuation specifically designed to connect two independent clauses into a sentence that isn’t a run-on.
EXAMPLEThe dog slept on the bed; he was tired.
Finally, you can fix this error by adding in a subordinating conjunction.
EXAMPLEThe 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 short 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.
Now you have a really good paragraph.
Now that you know how to fix these run-ons, you can also work on preventing 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 creating 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: