# Run-on sentences, comma splices and fragments

Canonical: https://duckyhelper.com/learn/grammar/run-on-sentences-and-fragments/
Updated: 2026-10-01

A run-on joins two complete sentences with nothing between them (a fused sentence) or with only a comma (a comma splice). Fix it with a period, a semicolon, a comma plus and, but or so, or a word like because. A fragment is a piece of a sentence written as if it were whole, usually missing a subject, a verb, or a main clause. Fix it by joining it to a nearby sentence or adding what is missing.

## What a complete sentence needs

A complete sentence, or **independent clause**, has a subject and a verb and makes sense on its own: *The bell rang.* A **dependent clause** has a subject and a verb but starts with a word like *because*, *when*, *although* or *if*, so it cannot stand alone: *when the bell rang*.

| Problem | Wrong | Right | Why |
| --- | --- | --- | --- |
| Fused sentence | *The game was canceled it rained all day.* | *The game was canceled because it rained all day.* | Two sentences ran together with nothing between them. |
| Comma splice | *The power went out, we lit candles.* | *The power went out, so we lit candles.* | A comma alone cannot join two sentences. |
| Fragment: dependent clause | *We stayed home. Because the road was closed.* | *We stayed home because the road was closed.* | *Because the road was closed* cannot stand alone. |
| Fragment: no main verb | *We stayed inside. Waiting for the storm to pass.* | *We stayed inside, waiting for the storm to pass.* | *Waiting* is not a main verb. Join it to the sentence before. |
| Fragment: no subject | *Mia studied for hours. And then went to bed.* | *Mia studied for hours and then went to bed.* | *And then went to bed* has no subject of its own. |

## Four ways to fix a run-on

1. **Period:** *The power went out. We lit candles.*
2. **Semicolon:** *The power went out; we lit candles.*
3. **Comma plus *and, but, or, so, yet, for, nor*:** *The power went out, so we lit candles.*
4. **Make one part dependent:** *When the power went out, we lit candles.*

> **Note: Long is not the same as run-on**
>
> A sentence can be long and correct, and a short one can be a run-on. *I ran she walked* is a run-on with four words. What matters is how the complete sentences are joined, not the length.

## Worked examples

**Example 1: find the two sentences**

Problem: *My phone died I couldn't call for a ride.*

1. Find each subject and verb: *phone died*, *I couldn't call*. Two complete sentences.
2. They are joined by nothing, so this is a fused sentence.
3. The second is a result of the first, so *so* shows the link.

Answer: *My phone died, so I couldn't call for a ride.*

**Example 2: attach a fragment**

Problem: *After the concert ended. We waited an hour for the bus.*

1. *After the concert ended* starts with *After*, so it is dependent and cannot stand alone.
2. Join it to the next sentence. Since it comes first, add a comma after it.

Answer: *After the concert ended, we waited an hour for the bus.*

## Common mistakes and fixes

| Mistake | Fix |
| --- | --- |
| Using *however* with a comma to join sentences | Use a semicolon: *It rained; however, we played.* |
| Starting a sentence with *Because* and stopping too soon | Finish the thought: *Because it rained, we stayed in.* |
| Splitting off an example with *For example* or *Such as* | *Such as apples and pears.* is a fragment. Join it to the sentence before. |
| Thinking every short sentence is a fragment | *Stop.* is complete: the subject *you* is understood. |

## Practice

**Five sentence boundary questions**

1. Which is a comma splice?
   A. When the power went out, we lit candles.
   B. The power went out, so we lit candles.
   C. The power went out, we lit candles.
   D. The power went out; we lit candles.

   Answer: The power went out, we lit candles.. Two complete sentences are joined by a comma alone. The others join them correctly with *so*, a dependent clause, or a semicolon.

2. Which is a sentence fragment?
   A. The road was closed.
   B. We stayed home because the road was closed.
   C. Because the road was closed.
   D. The road was closed, so we stayed home.

   Answer: Because the road was closed.. *Because* makes the clause dependent, so it cannot stand alone. The other three are complete sentences.

3. What is the best fix for this run-on? *The game was canceled it rained all day.*
   A. The game was canceled, it rained all day.
   B. The game, was canceled it rained all day.
   C. The game was canceled it, rained all day.
   D. The game was canceled because it rained all day.

   Answer: The game was canceled because it rained all day.. *Because* turns the second part into a dependent clause and shows the cause. A comma alone makes a comma splice, and the other two put commas in the wrong places.

4. Which correctly fixes the fragment? *We stayed inside. Waiting for the storm to pass.*
   A. We stayed inside; waiting for the storm to pass.
   B. We stayed inside, waiting for the storm to pass.
   C. We stayed inside. Waited for the storm to pass.
   D. We stayed inside, and waiting for the storm to pass.

   Answer: We stayed inside, waiting for the storm to pass.. Joining the phrase to the sentence with a comma makes one complete sentence. A semicolon needs a full sentence after it, *Waited for the storm to pass* has no subject, and *and waiting* has no verb to match *stayed*.

5. Which of these is a complete sentence?
   A. The tall man in the blue coat.
   B. After the movie ended.
   C. Running down the hall.
   D. Stop.

   Answer: Stop.. *Stop.* is a command, and commands have an understood subject, *you*. The others are missing a main verb or a main clause.

## Frequently asked questions

### Is a run-on the same as a long sentence?

No. A run-on is two or more complete sentences joined without correct punctuation. A long sentence can be perfectly correct if its parts are joined properly, and a very short one, like *I ran she walked*, can be a run-on.

### Are fragments ever okay?

Writers sometimes use a fragment on purpose for effect, like *Not again.* in a story or ad. Purdue OWL notes that in academic and other formal writing you should avoid them. In school essays and on tests, write complete sentences.

### What is the fastest way to check my essay for these errors?

Read it backward, one sentence at a time, from the last sentence to the first. Out of context, a fragment sounds unfinished, and a run-on sounds like two thoughts. Then check every comma that sits between two complete sentences.

## Sources

- [Purdue OWL, Sentence Fragments](https://owl.purdue.edu/owl/general_writing/mechanics/sentence_fragments.html), accessed 2026-10-01
- [Purdue OWL, Identifying Independent and Dependent Clauses](https://owl.purdue.edu/owl/general_writing/punctuation/independent_and_dependent_clauses/index.html), accessed 2026-10-01
- [Purdue OWL, Run-ons, Comma Splices, and Fused Sentences (exercise answers)](https://owl.purdue.edu/owl_exercises/sentence_structure/sentence_structure/run_ons_comma_splices_and_fused_sentences_answers.html), accessed 2026-10-01

## Related

- [Comma rules](https://duckyhelper.com/learn/grammar/commas/)
- [When to use a semicolon](https://duckyhelper.com/learn/grammar/semicolons/)
- [SAT punctuation: Boundaries questions](https://duckyhelper.com/learn/sat-reading-writing/boundaries-punctuation/)
- [Grammar study guides](https://duckyhelper.com/learn/grammar/)

## Try asking Ducky

- "Read my essay with me and stop at every sentence that might be a run-on."
- "Is this a fragment? Explain why, using my sentence."
- "Give me five run-ons and let me fix each one a different way."

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