A run-on sentence doesn’t separate any of its independent clauses with the punctuation that it needs, and a comma splice incorrectly separates two independent clauses with a comma, instead of a comma-and-coordinating-conjunction.
Practice this yourself on Khan Academy right now: https://www.khanacademy.org/syntax/e/recognizing-run-ons-and-comma-splices
Missed the previous lesson? Watch here: https://www.khanacademy.org/humanities/grammar/syntax/v/recognizing-fragments-syntax-khan-academy
Syntax on Khan Academy: Syntax is the ordering of language; it’s the study of how sentences work. In this section, we’ll scratch the surface of syntax as it applies to English grammar. Much more can be said about this subject, but we’ll save that for KA Linguistics.
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