What is a run-on sentence and how can you fix it

Do you ever stumble over a sentence that just keeps rolling, without a natural pause? That’s what writers call a run-on. It’s not a rare fault, and you’ve probably bumped into it many times in student essays, emails, or even ambitious social-media posts. Let me break down what a run-on is, why it trips readers up, and how to fix it so your writing feels clean and confident—whether you’re tackling the English section of a placement test or simply aiming for clearer communication.

What exactly is a run-on sentence?

At its heart, a run-on happens when two independent thoughts are joined in a single breath, without the right punctuation or connecting word. An independent clause is a mini-sentence that could stand on its own: it has a subject and a verb and expresses a complete idea. A run-on throws two of those complete thoughts together, and that muddles the flow.

There are two common varieties you’ll see:

• A fused sentence: two independent clauses crash into each other with no punctuation at all. Example: I love to read I have many books.

• A comma splice: two independent clauses are chained with just a comma, which isn’t strong enough to hold them together. Example: I love to read, I have many books.

Yes, the difference is subtle, but it matters. A reader should feel a clear break or a clear connector between ideas. When that connection is missing, the sentence can feel awkward, or it can blur the relationship between the ideas you’re trying to express.

Why run-ons sneak into our writing (and why they matter)

Write with rhythm—the rhythms of speech and breath—so readers don’t stumble. Run-ons interrupt that rhythm. They force the reader to pause and re-read, and not in a good way. That’s particularly true in the moments when you want to make a precise point or link two ideas that truly belong together.

In contexts like the English section of a placement test or other standard assessments, a clean sentence is a signal that you understand sentence structure and punctuation. But more than that, clean sentences help you communicate your ideas more persuasively, whether you’re describing a concept, comparing two points, or telling a short anecdote.

How to fix run-ons in a breeze

Here are practical, do-this-now options. Pick the one that fits your meaning and the tone of your writing. The key is to preserve the relationship between the ideas while giving the reader a clear path through your thoughts.

1. Split into two sentences

If the ideas are strong on their own, give them their own period.

• Before: The sun was setting I walked home.

• After: The sun was setting. I walked home.

2. Use a semicolon

A semicolon folds two related independent clauses into one clean, pause-free line. This works well when the ideas are closely connected.

• Before: The sun was setting, I walked home. (comma splice)

• After: The sun was setting; I walked home.

3. Use a comma plus a coordinating conjunction

FANBOYS (for, and, nor, but, or, yet, so) are the classic helpers here. They show how the ideas relate—addition, contrast, cause, result, etc.

• Before: The sun was setting, I walked home.

• After: The sun was setting, and I walked home.

You can also swap in but, so, or yet as it fits the sense you’re making.

4. Turn one clause into a dependent clause

If one of the thoughts doesn’t need to stand alone, make it dependent with a subordinating conjunction: because, while, since, although, etc.

• Before: I love to read, I have many books.

• After: I love to read because I have many books.

Note that this doesn’t always apply if both parts truly stand independently; in that case, options 1–3 are safer.

A few quick tips to spot run-ons before they slip through

• Read aloud. If you hit a place where your voice naturally wants a breath but you don’t see a punctuation mark, you may have a run-on.

• Watch for two independent thoughts in a row. If you can remove one part and still have a complete sentence, you’re likely dealing with a run-on when both parts are complete ideas.

• Look for comma splices in long sentences. If a sentence has more than one independent clause and only a comma between them, that’s a comma splice.

• Check for the two big culprits: fused sentences (no punctuation) and comma splices (comma, but no conjunction).

Examples you can relate to

Let’s look at a few everyday lines and see how to tidy them up.

• Fused sentence

Before: I finished my email I grabbed coffee.

After: I finished my email, and I grabbed coffee.

• Comma splice

Before: She loves photography, she also enjoys hiking.

After: She loves photography, and she also enjoys hiking.

Or: She loves photography. She also enjoys hiking.

• Subordinate when it helps

Before: I need to study I have a test tomorrow.

After: I need to study because I have a test tomorrow.

If you want a quick mental checklist, try this: Is there a subject and a verb on both sides of that potential break? If yes, you’re probably dealing with a run-on—unless you’ve got a strong, clearly used punctuation mark or conjunction.

Why this matters in real life writing

Clear writing wins. It makes your point feel confident, precise, and credible. It helps a reader stay with you from start to finish. And yes, in contexts like standardized language assessments, being able to recognize and fix run-ons is a mark of good grammar sense—one of those small, practical skills that add up.

A little digression for texture

Ever notice how authors handle longer sentences in novels? Some writers use a dash or a colon to insert a quick thought, almost like a breath. That can be a stylish way to connect two ideas without breaking the flow. Just be mindful—overusing dashes can turn your writing choppy, and too many long, explanatory phrases can dull the impact. The trick is balance: a well-placed dash or semicolon can sharpen your point, while a series of run-ons can dilute it.

A tiny, useful practice pack (without turning this into a workout)

If you’re skimming this after a long day and just want something simple to remember, keep these three rules in mind:

• Rule of two: If two complete thoughts show up, pause with a period, a semicolon, or a conjunction.

• The comma is not a bridge by itself. It needs a conjunction if you’re joining two complete thoughts.

• When in doubt, try turning the second clause into a dependent one, or make them two separate sentences.

Putting it into everyday writing

Here are three quick before/after pairs to illustrate how small changes improve clarity. You’ll see how easy it is to elevate your sentences with minimal effort.

1. Before: I like reading I also like writing.

After: I like reading, and I also like writing.

2. Before: The project was late, stakeholders worried.

After: The project was late, and stakeholders worried.

Alternative: The project was late. Stakeholders worried.

3. Before: She enjoys poetry it relaxes her.

After: She enjoys poetry because it relaxes her.

Notice how the after versions feel steadier, with a clearer link between ideas. It’s the same content, just a cleaner road for the reader’s eyes.

From basics to broader skills

Mastering run-ons isn’t just about dotting every i. It’s about shaping sentences that carry your meaning with ease. When you can present ideas as crisp, well-structured thoughts, you free up time to focus on what you’re really saying—whether you’re explaining a concept, making an argument, or telling a story.

If you ever stall on a sentence, try a quick “sentence surgery” approach:

• Identify the main idea in each clause.

• Decide how tightly those ideas should relate.

• Choose the punctuation that best mirrors that relationship.

Another little trick: vary your sentence length. Short sentences deliver punch. Medium ones carry nuance. A longer, carefully built sentence can weave a thought together without losing the reader. The goal is a dynamic rhythm, not a string of robotic lines.

In the bigger picture

Writing well isn’t about chasing perfection. It’s about making your thoughts legible and engaging. Run-ons are not the end of the world, but they’re a small, telltale sign that a sentence could be clearer. Fixing them—by splitting, connecting, or reworking—gives your ideas room to breathe.

If you’re exploring English language topics tied to placement assessments or just aiming to sharpen your literacy, think of run-ons as a doorway. It’s a doorway to better punctuation, smarter sentence structure, and more confident communication. And once you’ve walked through it, you’ll likely notice other tiny gaps you can tidy up with the same straightforward tools.

A final nudge

Every writer has room to improve, and that’s not a fault—it’s a sign you’re growing. Start with the basics, keep a light touch, and don’t be afraid to revise. The moment you hear a sentence that feels too long or a little awkward, you’ve got a chance to tune it up. Before you know it, you’ll be reshaping paragraphs with the same ease you once reserved for reading a great book.

If you’ve come across run-on sentences in your reading or writing, you’re in good company. They’re common, they’re correctable, and they’re a straightforward way to boost clarity. With the small adjustments outlined here, you’ll be better equipped to express your ideas clearly—on the page and in conversation. And that clarity—the ability to connect thoughts with intent—will serve you long after any test or course ends.