A run-on sentence joins two or more complete thoughts without the punctuation or connecting words they need. You can usually fix one by separating the thoughts, adding a conjunction, or using a semicolon.
Four easy ways to fix a run-on sentence
Suppose the original sentence is:
The meeting ended late I missed my train.
1. Split it into two sentences
The meeting ended late. I missed my train.
This is often the clearest option, especially when both ideas are equally important.
2. Add a comma and a coordinating conjunction
The meeting ended late, so I missed my train.
Use a comma before for, and, nor, but, or, yet, or so when the conjunction connects two complete sentences. The conjunction should show the relationship between the ideas:
- and adds information
- but or yet shows contrast
- so shows a result
- for gives a reason
- or presents an alternative
3. Use a semicolon
The meeting ended late; I missed my train.
A semicolon works when the thoughts are closely related and you do not need a connecting word. Both sides of the semicolon must be complete sentences.
You can also use a transition:
The meeting ended late; therefore, I missed my train.
Common transitions include however, therefore, meanwhile, instead, consequently, and nevertheless.
4. Make one thought dependent on the other
Because the meeting ended late, I missed my train.
This method helps clarify which event caused or influenced the other. Useful connecting words include because, although, when, while, if, since, and unless.
Quick way to identify a run-on
Look for a place where one complete sentence ends and another begins. Ask whether each part could stand alone:
- “The meeting ended late.” — complete
- “I missed my train.” — complete
If they are joined with no punctuation—or with only a comma—the sentence needs revision. Joining two complete sentences with only a comma creates a related error called a comma splice:
Incorrect: The meeting ended late, I missed my train.
Correct: The meeting ended late, so I missed my train.
Reusable editing prompt
To have ChatGPT revise a specific sentence while preserving its meaning, use:
Fix the run-on sentence below. Keep the original meaning and tone. Provide three versions: one using separate sentences, one using a conjunction, and one using a semicolon.
Sentence: [Paste sentence here]
Choose the version that best matches the intended rhythm. Separate sentences sound direct, conjunctions make the logical relationship explicit, and semicolons create a slightly more formal flow.