A run-on sentence is actually two complete sentence stuck together, either with just a comma or with no punctuation at all.
Conjunctions connect clauses to show continuity, cause-and-effect, contrast, or the sequence of events.
WRONG: The children had been playing in the park, they were covered with mud.
WRONG: The children had been playing in the park they were covered with mud.
How to correct run-on sentences:
- Use a conjunction.
RIGHT: The children had been playing in the park, so they were covered with mud.
- Join the clauses with a semicolon.
RIGHT: The children had been playing in the park; they were covered with mud.
- Make one of the clauses subordinates.
RIGHT: Because the children had been playing in the park, they were covered with mud.
RIGHT: The children were covered with mud because they had been playing in the park.
- Combine the two independent clauses into one independent clause.
RIGHT: The children had been playing in the park, and they were covered with mud.
- Create two separate sentences.
RIGHT: The children had been playing in the park. They were covered with mud.
** Be careful with words like accordingly, however, meanwhile, and therefore. These words cannot be used with a comma to join independent clauses. Yet they can be used with a semicolon to join independent clauses.