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August 9, 2023

How to Fix Run-On Sentences (With Help From AI)

How to Fix Run-On Sentences (With Help From AI)

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I don't know if you've ever gotten criticism about using run-on sentences as a child, but I sure have.

Now that I am a professional editor, I can tell you the good news: avoiding run-on sentences is easy, you just need a bit of practice.

In this article, I’ll share how you can use AI, plus some additional tips, to make sure your content stays short and to the point.

What Are Run-On Sentences?

Technically, a run-on sentence is a specific grammatical error where you include more than one independent clause without the use of both a comma and a coordinating conjunction to separate them.

I'll explain the technical terms in the next section. But first, let’s see a run-on sentence example.

There is a hole in my bucket, Liza will fix it.

This is a common type of run-on called a comma splice. A less common example is the fused sentence, below.

Henry is clueless he won’t be able to do it.

You might also see any sentence that is extremely long, confusing, and complicated called a run-on sentence. While these might not fit the technical definition of run-on sentences, they can still be an issue. Any sentence that is lengthy and hard to pick apart can slow readers down and leave them missing your point.

How to Identify a Run-on Sentence

To fix a run-on sentence, you first need to know how to spot one.

Run-on sentences include more than one independent clause connected without the correct punctuation and conjunctions. But what is an independent clause?

In English, a clause is a part of a sentence that includes two things:

  • A subject: a person, place, or thing that is performing an action (in bold below).
  • A verb: an action (underlined below).

Clauses that are also complete sentences are independent clauses

  • the ball rolled
  • Dee shoves her brother
  • it was raining

Clauses that are designed to add context to another part of a sentence are dependent clauses

  • as the ball rolled
  • when Dee shoves her brother
  • before it was raining

Note the addition of dependent marker words at the beginning of the sentence. These words turn a complete sentence into a phrase that describes something about how something else is happening. You may notice that dependent clauses feel like unfinished pieces of information. Here, we’re left wondering, what happens when Dee shoves her brother? 

If you’re trying to figure out whether your sentence is a run-on, see if it fits these criteria:

  1. There is more than one subject-verb pair.

  2. You can cut these phrases into separate sentences without feeling like something's missing.

  3. You are missing a comma, a coordinating conjunction (for, and, nor, but, or, yet, so) or both.

In the Wordtune editor, grammar errors are underlined in red. If you see an error, check these criteria to discover if it's a run-on.

Screenshot of a grammatical error highlighted in red in the Wordtune editor.

Why Fixing Run-On Sentences Is So Important

If they just represent several complete sentences smashed together, why bother correcting run-on sentences?

The most important reason to fix your run-ons is to improve readability. Punctuation exists partly to enable readers to get your message as clearly and easily as possible. As people often skim articles rather than reading them closely, the correct commas and conjunctions can signal to them when to pay attention. Long sentences, or those that run together, risk readers zoning out and missing important details.

Plus, in most academic and professional contexts, proper punctuation signals to your audience that you are knowledgeable, reputable, and trustworthy. You’re essentially demonstrating that you are educated, able to follow professional industry standards, and willing put in the effort to polish your work.

Four Simple Ways to Fix a Run-On Sentence

Now that you can identify them, here are some examples of how to fix run-on sentences.

1. Split it into two sentences.

The simplest way to fix a run-on is to separate the two independent clauses into two single sentences. 

She likes to play soccer, she also likes to swim.

✔️She likes to play soccer. She also likes to swim.

2. Add one of the other punctuation marks that separate complete sentences.

There are three more punctuation options for adding a long pause between complete sentences: the em dash ( ), the semicolon ( ; ), and the colon ( : ). These show varying degrees of relatedness between the two clauses, so choose one that fits.

There's a hole in my bucket, Liza will fix it.

✔️There's a hole in my bucket; Liza will fix it.


Henry can't do it he is clueless.

✔️Henry can't do it he is clueless!


Henry can’t do it he doesn’t know how to use a saw.

✔️Henry can’t do it: he doesn’t know how to use a saw.

3. Add a coordinating conjunction and a comma.

If you don’t already have one, add a comma between the two clauses. After the comma, you must also include one of the coordinating conjunctions. There are only seven coordinating conjunction options, so if you aren’t sure what to add, think of the acronym FANBOYS:

  • For
  • And
  • Nor
  • But
  • Or
  • Yet
  • So

Each of these affects the meaning of the sentence, so choose one that complements what you want to say.

Mitzy sat on her pillow, a spider scared her away.

✔️ Mitzy sat on her pillow, but a spider scared her away.

4. Check your grammar with Wordtune.

If you're writing in the Wordtune editor and notice a run-on sentence, place your cursor over the red-underlined phrase and Wordtune will suggest some options for fixes. It may also suggest more complex sentences with dependent clauses. You can edit these to fit your writing style while keeping correct grammar in mind.

Screenshot of the Wordtune editor’s suggestions to correct grammar in a run-on sentence.

Mary had a little lamb, everywhere she went it would follow her.

✔️ Mary had a little lamb. Everywhere she went, it would follow her.

Four Strategies to Avoid Long Sentences

Even if they aren’t technically run-on sentences, lines with lengthy combinations of clauses and parentheticals are likely to confuse readers and be a drag to read. 

You may want to rephrase if your sentence takes up more than two or three lines on a Google doc, Word Doc, or browser app. On a mobile device, break up sentences of more than three or four lines. More than four or five punctuation marks in a sentence could also signify that shortening is needed.

Once you’ve determined your sentence is too long, here are a few ways to slash your word count.

1. Cut the fluff.

Fluffy writing is when your sentence includes many words that don’t contribute to the overall meaning. Repetition, wordy clichés, extra connector words, passive voice, and unneeded interjections can all be culprits.

Reread your sentence to check if every word is strictly necessary. Are you saying the same thing twice? 

Are there many pairs of two short words, like which are, it is, or that which? While there’s nothing wrong with these pairs, I’ve noticed they can often be rephrased in simpler ways.

When we reread and double-check our own work, it is often the case that sentences are found which are repetitive and wordy.

✔️ When we reread our own work, we often find repetitive sentences.


2. Focus on powerful verbs.

Robust verbs can boost sentences by making them more impactful with fewer words. 

If you find yourself using the bland verb to be a lot — its many forms include is, are, was, and were — look for another action word hiding in your sentence that could become the main verb instead.

Most sentences can be energized by a robust verb.

✔️ Robust verbs energize sentences.


3. Check your punctuation.

If you have a long sentence that includes many clauses, commas, or coordinating conjunctions (remember the FANBOYS), try taking out some of the clauses to see if they could become a new sentence. It can help to pick out phrases already separated from the rest of the sentence by commas or parentheses.

The weather forecast (which was wrong yet again) predicted sunny skies, but when I stepped outside I found it was pouring, a grey curtain obscuring all but the nearest objects.

✔️ The weather forecast predicted sunny skies, but when I stepped outside I found it was pouring. They'd been wrong yet again. A grey curtain obscured all but the nearest objects.


4. Use Wordtune's “Shorten” function.

In the Wordtune editor, highlight your too-long sentence and select “Shorten.” Wordtune will then provide you with a list of alternative sentences. Keeping correct grammar in mind when you use this tool is useful, as this will help you to select and tweak the option that best supports your style and meaning.

A screenshot of the Wordtune editor's suggestions when using the Shorten tool.

The Wordtune platform is designed to help you optimize and improve your sentences by providing suggestions for how to write in a casual or formal tone, spices, such as adding examples or statistical facts, and how to shorten or expand sentences.

✔️ Wordtune offers suggestions for writing in a casual or formal tone, incorporating examples or statistical facts, and reducing or expanding sentences.

Wordtune provides a simple tool for shortening sentences at the push of a button. But to strengthen your writing, it’s important to understand the underlying grammatical structures yourself.

Check sentences that are flagged by Wordtune for grammar, as well as those that run over two lines in your word processor, or those that have multiple subject + verb combos and little punctuation. Look for ways to pull out independent clauses from these and make them into their own sentences. Or, if they’re short enough, just add a comma and one of our FANBOYS.

Wordtune's tools can give you suggestions, double-check your instincts, and reinforce what you’ve learned. Working alongside AI, you can improve your grammar and get your message across to readers clearly.

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