Run-on Sentences: the rule, with examples
A run-on sentence joins two or more complete thoughts with no punctuation or joining word. Fix it by adding a period, a semicolon, or a comma plus a conjunction between the clauses. Paste your own sentence into the free checker below to fix it in one click.
A run-on sentence joins two or more complete thoughts with no punctuation or joining word. Fix it by adding a period, a semicolon, or a comma plus a conjunction between the clauses.
How it works
- 1Spot the pattern. Read the sentence aloud. If you naturally pause where there’s no punctuation — and the part after the pause could stand alone — you’ve found a run-on.
- 2Apply the rule. Separate the clauses: end the first with a period, link them with a semicolon, or add a comma and a conjunction (and, but, so).
- 3Check your sentence. Paste your text into the grammar checker below — it flags the issue and shows the correction.
- 4Re-read it. Read the corrected version aloud to confirm it says exactly what you meant.
The rule
When two independent clauses run together without any punctuation or coordinating conjunction, the sentence is a run-on (also called a fused sentence). Each clause needs proper separation.
How to spot it
Read the sentence aloud. If you naturally pause where there’s no punctuation — and the part after the pause could stand alone — you’ve found a run-on.
How to fix it
Separate the clauses: end the first with a period, link them with a semicolon, or add a comma and a conjunction (and, but, so).
The most common mistake
Confusing length with run-ons. A long sentence can be perfectly correct; a short one (“I love coffee I drink it daily”) can still be a run-on. If you’re not sure whether your sentence has the problem, paste it into the checker above — it catches this and explains the fix in plain language.
| ❌ Incorrect | ✓ Corrected | Why |
|---|---|---|
| I love coffee I drink it daily. | I love coffee. I drink it daily. | Period separates the clauses |
| The bus was late she missed class. | The bus was late, so she missed class. | Comma + conjunction |
| He trained hard he won the race. | He trained hard; he won the race. | Semicolon links related clauses |
Frequently asked questions
What is a run-on sentence?
Two or more complete sentences fused with no punctuation or joining word — for example, “It rained all day we stayed inside.” It needs a period, semicolon, or conjunction.
What’s the difference between a run-on and a comma splice?
A run-on has no punctuation between the clauses; a comma splice has a comma but no conjunction. Both are fixed the same three ways.
How do I check my own writing for this?
Paste your text into the free grammar checker on this page. It flags the issue, suggests a correction, and explains why — so you learn the rule, not just the fix.
Is it free?
Yes — 3 free runs every day with up to 500 words per run, no credit card to start. Upgrade for a larger word pool, or use the free iOS app.