A run-on sentence joins two complete sentences with nothing between them; a comma splice joins them with only a comma. Both are wrong — and both have the same easy fixes. They’re among the most common writing errors, and a spell checker won’t flag them. Here’s how to spot and fix them.
Spot the problem
First, find two independent clauses — each a complete sentence that could stand alone.
- Run-on (fused): “It was late we went home.” (nothing joins them)
- Comma splice: “It was late, we went home.” (only a comma — not enough)
If both halves could be their own sentence, a comma alone can’t hold them together.
Four ways to fix both
Take “It was late, we went home.” Any of these is correct:
- Period — make two sentences: “It was late. We went home.”
- Semicolon — for closely related ideas: “It was late; we went home.” (See semicolons and colons.)
- Comma + coordinating conjunction (and, but, so, or, yet): “It was late, so we went home.”
- Subordinate one clause: “Because it was late, we went home.”
Pick the one that best fits the relationship between the ideas — option 3 or 4 usually reads most naturally.
Why they happen
Comma splices creep in when two thoughts feel connected, so a comma seems right. It isn’t — a comma can’t join two complete sentences on its own. Run-ons happen when ideas pour out faster than punctuation. Both are easy to miss in your own draft.
Catch them automatically
This is exactly what a context-aware checker is for: run your text through the grammar checker and it flags comma splices and run-ons so you can apply one of the four fixes. If you find a lot of very long sentences, the readability checker will point them out, and the paraphraser on Shorten mode can break a tangled one into clean pieces.
Learn to spot two independent clauses, choose the right join, and these errors disappear from your writing.
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