A run-on sentence is any sentence in which two independent clauses are improperly joined. An independent clause is anything that could stand on its own as a full sentence. Consider the following:
I know, you know.
"I know" and "you know" are both independent clauses, so this is incorrect. There are several ways to fix a run-on sentence:
- Add a semicolon, which is used to separate independent clauses: I know; you know.
- Add a conjunction: I know, and you know.
- Make one of the clauses subordinate/dependent: I know that you know. Or, Whatever I know, you know.
In this case, "while driving to dinner" is not a dependent clause, but rather a modifying phrase, so it's perfectly acceptable to attach it to the independent clause "Fred lost his wallet."
Ceilidh Erickson
EdM in Mind, Brain, and Education
Harvard Graduate School of Education