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Run-on Sentences and Comma Splices

Lucas Fink
Lesson by Lucas Fink
Magoosh Expert
Summary
Run-on sentences and comma splices appear regularly on ACT English, so fixing them quickly and accurately is essential. The key is to recognize when two complete sentences are joined incorrectly and then choose one of four valid fixes, using the cover-up test to confirm the error is gone.
  • A run-on sentence joins two complete sentences with no punctuation, while a comma splice joins them with only a comma.
  • One fix is to separate the ideas into two sentences with a period; another is to use a conjunction, either a comma plus a FANBOYS coordinating conjunction or a subordinating conjunction such as because, although, since, when, while, or as.
  • A semicolon correctly links two closely related complete sentences, but it should not be paired with a FANBOYS word; however and therefore can follow a semicolon because they are not coordinating conjunctions.
  • A frequently missed fix is to turn the second sentence into a describing phrase by using which, whose, of which, or by reducing it to a phrase with an -ing or similar modifier.
  • The quickest way to check a possible fix is the cover-up test: if the words after the comma can still stand alone as a complete sentence, the comma splice remains.
  • On ACT questions, wrong answers often keep two full sentences connected by only a comma, misuse however or therefore like FANBOYS words, or add extra subjects after which; strong answers correctly make one part dependent or attach it as a modifier.
Chapters
00:00
Identifying Run-Ons and Comma Splices
01:00
Four Reliable Ways to Fix the Error
05:25
Applying the Rules to ACT-Style Questions
09:30
Core Takeaways for Test Day