Run-On Sentences: How to Identify and Fix Them

Run-on sentences are among the most common grammatical errors in English writing. They occur when two or more independent clauses are joined without proper punctuation or connecting words. While run-on sentences might seem like a minor issue, they can significantly reduce the clarity and readability of your writing. This comprehensive guide will help you understand what run-on sentences are, recognize them in your own writing, and master four effective methods for fixing them.

What Is a Run-On Sentence?

A run-on sentence occurs when two or more independent clauses (complete thoughts that could stand alone as sentences) are joined together without appropriate punctuation or conjunctions. The term "run-on" refers to the way one clause "runs into" the next without a proper boundary between them.

It's important to understand that a run-on sentence is not simply a sentence that is too long. A perfectly grammatical sentence can be quite lengthy, while a run-on sentence might be relatively short. The issue is not length—it's the absence of proper connection between independent clauses.

Types of Run-On Sentences

There are two main types of run-on sentences, and understanding the distinction helps you fix them more effectively.

1. Fused Sentences

A fused sentence (also called a "true" run-on) occurs when two independent clauses are joined with no punctuation at all between them.

In each of these examples, two complete sentences have been fused together without any punctuation separating them. The reader has to figure out where one thought ends and the next begins, which slows down comprehension.

2. Comma Splices

A comma splice occurs when two independent clauses are joined by only a comma, without a coordinating conjunction. While a comma splice technically uses punctuation, a comma alone is not strong enough to join two independent clauses.

Comma splices are sometimes considered a separate category from run-on sentences, but many grammar guides treat them as a subcategory of run-ons because the underlying problem is the same: two independent clauses are not properly connected.

Why Run-On Sentences Are Problematic

Run-on sentences create several problems for readers and writers alike:

• Reduced clarity: When clause boundaries are unclear, readers must re-read sentences to determine where one idea ends and another begins.
• Confused relationships: Without proper connectors, the logical relationship between clauses (cause/effect, contrast, addition) is lost.
• Loss of emphasis: Important ideas get buried when they run together without proper separation.
• Unprofessional appearance: In academic and professional writing, run-on sentences signal a lack of editing and grammatical awareness.
• Reading fatigue: Continuous text without proper pauses exhausts the reader and reduces engagement.

How to Identify Run-On Sentences

Follow these steps to check for run-on sentences in your writing:

1. Find the main clauses. Identify each subject-verb pair in the sentence. If you find two or more independent clauses, check how they are connected.
2. Check the connection. Look for a coordinating conjunction (for, and, nor, but, or, yet, so), a semicolon, or a period between the clauses. If none of these is present, you have a run-on.
3. Watch for comma-only connections. If two independent clauses are connected by only a comma (no conjunction), you have a comma splice.

Four Methods to Fix Run-On Sentences

There are four standard ways to correct a run-on sentence. Each method is appropriate in different situations, and varying your approach will improve the rhythm and style of your writing.

Method 1: Use a Period (Create Two Sentences)

The simplest fix is to separate the independent clauses into two distinct sentences using a period.

This method works best when the two clauses are separate ideas that don't need a close connection, or when you want to create emphasis through shorter sentences.

Method 2: Use a Semicolon

A semicolon connects two closely related independent clauses. Use this method when the two ideas are tightly linked and you want to show that connection.

You can also use a semicolon with a conjunctive adverb (however, therefore, moreover, consequently, etc.) followed by a comma:

Method 3: Use a Comma and Coordinating Conjunction

Add a comma followed by one of the seven coordinating conjunctions (remembered by the acronym FANBOYS: for, and, nor, but, or, yet, so) between the clauses.

Choose the conjunction that best expresses the relationship between the clauses. "But" shows contrast, "and" shows addition, "so" shows cause/effect, and so on.

Method 4: Subordinate One Clause

Transform one of the independent clauses into a dependent clause by adding a subordinating conjunction (because, although, when, since, if, while, etc.).

This method is particularly effective when one clause provides context or a reason for the other, creating a clearer logical relationship between the ideas.

Comprehensive Examples

Run-On Sentence	Fix (Method)	Corrected Version
"I woke up late I missed the bus."	Subordination	"Because I woke up late, I missed the bus."
"She sings beautifully he plays guitar."	Comma + conjunction	"She sings beautifully, and he plays guitar."
"The food was cold, we ate it anyway."	Semicolon	"The food was cold; we ate it anyway."
"They won the game they celebrated all night."	Period	"They won the game. They celebrated all night."
"I need coffee, I'm exhausted."	Subordination	"I need coffee because I'm exhausted."

Common Mistakes to Avoid

Mistake 1: Using "However" with Only a Comma

Conjunctive adverbs like "however," "therefore," "moreover," and "consequently" are not coordinating conjunctions. They need a semicolon before them (or a period), not just a comma.

Mistake 2: Adding a Comma Without a Conjunction

Mistake 3: Thinking Length Determines Run-Ons

A common misconception is that any long sentence is a run-on. This is false. A sentence can be very long and perfectly grammatical if all its clauses are properly connected. Conversely, a very short sentence can be a run-on:

Long Sentences vs. Run-On Sentences

It bears repeating: length and correctness are separate issues. A long sentence is not automatically a run-on, and a run-on is not automatically long. The difference lies in how clauses are connected, not in how many words the sentence contains.

Professional writers regularly compose long, complex sentences that are perfectly grammatical. These sentences use coordinating conjunctions, subordinating conjunctions, relative pronouns, and proper punctuation to connect multiple clauses into a coherent whole.

That said, even if a long sentence is grammatically correct, it may still benefit from being broken into shorter sentences for readability. Sentence variety—mixing short, medium, and long sentences—is a hallmark of good writing.

Practice Exercises

Identify whether each sentence below is correct or a run-on, then fix any run-ons using any appropriate method:

1. "The train was delayed we waited on the platform for an hour."
2. "She loves painting, and she spends every weekend at her studio."
3. "The storm knocked out the power, we lit candles."
4. "Because the road was icy, the school buses were delayed."
5. "He packed his bags he called a taxi he headed to the airport."

Summary and Quick Reference

Here is a quick-reference guide for identifying and fixing run-on sentences:

Fix Method	When to Use	Example
Period	Ideas are separate; want emphasis	"She left. He stayed."
Semicolon	Ideas are closely related	"She left; he stayed."
Comma + FANBOYS	Show specific relationship	"She left, but he stayed."
Subordination	One idea depends on the other	"Although she left, he stayed."