How it works. Decide whether each group of words is a complete sentence, a fragment, or a run-on. Strong writers fix fragments and run-ons. 16 per round, instant feedback.
Complete sentence: has a subject and a verb and expresses a full idea ("The dog barked.").
Fragment: a piece missing a subject or verb, or not a full idea ("Running fast.").
Run-on: two sentences jammed together with no proper join ("I was tired I slept.").