Sentence Structure
Run-on sentences and comma splices
Two complete sentences need more than a comma between them.
Why this happens
Run-on sentences (fused sentences) jam two or more independent clauses without correct punctuation or conjunction. Comma splices are the most common type — a comma where a period, semicolon, or coordinator belongs. They often appear when writers rush through related ideas and assume the link is obvious. In timed exams, fixing a run-on is faster when you first mark each subject–verb pair, then choose a period, semicolon, or conjunction that matches the logic.
See it in a sentence
IncorrectThe experiment failed the team redesigned the method.
CorrectThe experiment failed, so the team redesigned the method.
Teaching note: Two complete clauses need a conjunction, semicolon, or full stop.
IncorrectShe proofread the essay, she submitted it online.
CorrectShe proofread the essay, and she submitted it online.
Teaching note: Comma alone cannot join two independent clauses — add and or use a semicolon.
IncorrectResults improved however bias remained.
CorrectResults improved; however, bias remained.
Teaching note: However between full clauses needs stronger punctuation than a lone comma.
More examples
I came, I saw, I conquered.
Asyndeton can work rhetorically in literary writing; examiners usually prefer explicit links.
The study was small; it still offered useful insights.
Semicolon fixes a run-on when clauses are closely related.
Join with subordination: Because results improved, we published early.
Making one clause dependent removes the run-on without two equal mains.
Not a run-on: She smiled and left.
One subject, two verbs — compound predicate, not two independent clauses.
Quick check
The deadline passed everyone submitted late work.
Show the fix
The deadline passed, and everyone submitted late work — or use a semicolon or period. Two independent clauses cannot fuse without punctuation.
Practice this topic in Wrytesmart
Open the grammar workspace to complete interactive exercises for run-on sentences and comma splices. You will spot errors, fill blanks, and transform sentences — always with teaching notes that explain the principle, not just the correction.
Master run-on sentences and comma splices in context
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