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Eliminate the Most Common Syntax Error: Run-On Sentences

Updated: Nov 27, 2021

A common grammar mistake that many writers make is the usage of comma splices and other means to create run-on sentences.

What is a run-on sentence?

A run-on sentence occurs when two complete, independent sentences are joined together through an incorrect manner. These are also sometimes called "fused sentences". Additionally, the length of a sentence does not determine if a sentence is a run-on or not. Very short, brief sentences could actually suffer the same error.

Below, let's review some of the most common types of run-ons!


Type #1: The Fuse

In this type of run-on, two independent sentences are fused into one without any sort of punctuation. It's usually pretty easy to recognize this issue by simply reading the sentence out loud. There's no natural break indicated by punctuation where you'd expect there to be.

For example:

I usually cook dinner I like making pasta.

It's clear that some form of punctuation should fall between "dinner" and "I".


Type #2: The Fuse w/ Conjunction

A coordinating conjunction (which you can remember by the easy acronym FANBOYS: for, and, nor, but, or, yet, so) is a word that connects two sentences. While it can be used to make a correctly punctuated sentence, many times, it is used incorrectly. Thus, this forms a run-on sentence.

For example:

I usually cook dinner and I like making pasta.

This kind of sentence is a bit more difficult to recognize as a run-on sentence, since when reading it out loud, it flows better than the first type above. However, it should be noted that whenever you use a coordinating conjunction to combine two complete sentences, you should always place a comma before it. Only then will it be punctuated in a grammatically correct manner. (An example will be given below!)


Type #3: The Comma Splice

Out of all the types of run-on sentences, comma splices are perhaps the most common. The name is rather self-explanatory: a comma splices between two complete sentences, combining them into one.

For example:

I usually cook dinner, I like making pasta.

When reading this out loud, it sounds natural, considering that a comma indicates a natural pause, despite the fact that this is technically incorrect.

While editing or writing, an easy method to catch comma splices is to read the two halves of the sentences by themselves. "I usually cook dinner." and "I like making pasta." sound independent on their own; thus, joining them by a comma is incorrect.

Think of the comma as far too weak to join a sentence.

The comma splice can also sneak into sentences that you add conjunctive adverbs into. Here is a list of common conjunctive adverbs:

Credit: RMIT University

For example:

I usually cook dinner, particularly, I like making pasta.

Writers can often mistake conjunctive adverbs for coordinating conjunctions (the FANBOYS). When using a conjunctive adverb like such, the sentence is considered a comma splice, since two complete sentences are joined together by a weak comma: "I usually cook dinner." and "Particularly, I like making pasta."


Now that we've gone over the three most common types of run-on sentences, let's discuss how to fix them. Most times, a run-on sentence can be corrected through slight, easy adjustments to the punctuation.


Solution #1: Use a Period

The good ol' period provides an easy fix.

I usually cook dinner. I like making pasta.

Easy, right?

Do note that if a sentence is not a run-on sentence, and a period is used instead of a comma, this can form a fragment, which is also grammatically incorrect (e.g. "Although I like cooking dinner, I get tired of making pasta." If you split this into "Although I like cooking dinner. I get tired of making pasta." the first sentence is a fragment.) We'll go over fragment sentences in another blog post, but beware of fragments for now!


Solution #2: Use a Semicolon

A period usually indicates a longer pause than a semicolon. As a result, a semicolon can be useful for fixing comma splices, where you may not want a strong, solid pause.

Take, for example:

I usually cook dinner; I like making pasta.

Isn't that a briefer pause than using a period?

A semicolon is also usually used to connect two similar, related ideas. In this example, dinner and pasta is indeed closely related. Consequently, using a semicolon would be rather appropriate, compared to a scenario like "I usually cook dinner; my dog is barking." which might not make as much sense.


Solution #3: Use a Comma (for the Fuse w/ Conjunction)

To solve the second type of run-on described above, use a comma before the coordinating conjunction.

I usually cook dinner, and I like making pasta.

Once you put a comma there, the sentence is considered grammatically correct.

Do note that a coordinating conjunction does not require a comma ahead of it in all cases. For example, "I don't cook breakfast nor lunch" does not require a comma ("I don't cook breakfast, nor lunch") since "lunch" is not a complete sentence. A comma is only required when a conjunction connects two complete sentences.


Solution #4: Use a Subordinating Conjunction

Here is a list of the most common subordinating conjunctions.

Credit: RMIT University

Using a subordinating conjunction is a great way to both fix improper punctuation and add variety to your syntax.

For example:

Since I usually cook dinner, I like making pasta.

Adding a subordinating conjunction makes part of your sentence dependent ("Since I usually cook dinner"). As a result, combining it with a complete sentence will not make it a comma splice or run-on sentence!

Make sure to include a comma after the dependent phrase, if the dependent phrase comes first, though. "Since I usually cook dinner I like making pasta" is not correct punctuation. On the other hand, if your dependent phrase comes after the independent one, you don't need a comma (e.g. "I like making pasta since I usually cook dinner.").


Now that we've gone through the types of run-ons and solutions, do you feel confident over your comprehension of them? Leave a comment below if you have any questions or need for clarification.

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