Fixing Run-Ons — I can fix a run-on using punctuation, conjunctions, or restructuring into separate sentences.

Why Sentences Need Boundaries

For thousands of years, people have searched for the best ways to organize written language. In the earliest forms of writing, there were no spaces between words, no commas, and no periods. Ancient Greek and Latin texts were written in a style called scriptio continua (continuous script), which meant every letter ran together without any breaks. Imagine trying to read an entire novel where nothing was separated — it would be exhausting! Over the centuries, writers and grammarians developed punctuation marks and sentence rules to make reading easier and meaning clearer.

The core question behind this lesson is simple: What happens when two complete thoughts crash into each other without the right punctuation or connector? The answer is a run-on sentence — and learning to fix run-ons is one of the most practical writing skills you can develop.

Core Principles & Definitions

Before you can fix a run-on, you need to understand a few building blocks. An independent clause is a group of words that contains a subject and a verb and expresses a complete thought — it can stand alone as a sentence. A run-on sentence occurs when two or more independent clauses are joined incorrectly, either with no punctuation at all (called a fused sentence) or with just a comma and no conjunction (called a comma splice).

Visualizing Run-Ons and Their Fixes

The diagram above is your roadmap for the rest of this lesson. Every time you spot a run-on, you have three tools in your toolbox. The trick is choosing the right one for the situation. Sometimes a simple period works best, sometimes a conjunction adds meaning, and sometimes restructuring creates a more sophisticated sentence. Let's dig into each strategy.

How Each Fix Strategy Works

Strategy 1: Punctuation (Period or Semicolon)

The simplest way to fix a run-on is to place a period between the two independent clauses and capitalize the next word. This creates two separate sentences. If the two ideas are closely related and you want to signal that connection, you can use a semicolon instead. A semicolon says, "These ideas are connected, but each one is still its own complete thought." You can also follow a semicolon with a conjunctive adverb (a transition word like however, therefore, or moreover) plus a comma.

Strategy 2: Comma + Coordinating Conjunction (FANBOYS)

A comma by itself cannot join two independent clauses — that creates a comma splice. But a comma plus one of the seven FANBOYS words (For, And, Nor, But, Or, Yet, So) is strong enough to hold two clauses together. The conjunction also adds meaning: but shows contrast, so shows cause and effect, and and shows addition.

Strategy 3: Restructure with a Subordinating Conjunction

Sometimes the best fix is to show that one idea depends on the other. By adding a subordinating conjunction (such as because, although, when, if, since, or while), you turn one independent clause into a dependent clause. A dependent clause cannot stand alone, so it can no longer form a run-on. When the dependent clause comes first, follow it with a comma. When it comes second, you usually do not need a comma.

The FANBOYS Toolkit & Subordinating Conjunctions

Worked Example: Fixing a Run-On Three Ways

Let's take one run-on sentence and fix it using all three strategies. This will show you how different fixes change the tone and emphasis of your writing.

Strengths & Limitations of Each Strategy

Each fix strategy has its own strengths and limitations. Knowing when to use each one will make your writing more varied and effective.

Connection to Advanced Sentence Structure

Fixing run-ons is not just about avoiding errors — it is the gateway to understanding more advanced sentence structures. Once you are comfortable identifying independent and dependent clauses, you can build compound sentences (two independent clauses joined correctly), complex sentences (an independent clause paired with a dependent clause), and even compound-complex sentences (multiple independent and dependent clauses combined). These more advanced structures are what separate basic writing from compelling, college-level prose.

As you move into more advanced English courses and begin writing essays, research papers, and creative pieces, your ability to vary sentence structure will directly affect your writing score and reader engagement. The skills you practice in this lesson — identifying clauses, choosing connectors, and adjusting punctuation — are the foundation of everything that comes next.

Practice Problems

Run-On Fixes at a Glance