Glossary
run-on sentence
A run-on sentence joins two independent clauses with no punctuation at all, while a comma splice joins them with only a comma.
A run-on sentence is two complete sentences written as one, with nothing between them: the pump alarmed the nurse checked the line. Both halves have a subject and a verb, and both could stand alone, so the run-on is a missing boundary rather than a missing word. It has two forms, and the exam uses both names. Fused, the clauses simply run together with no mark. Joined by a comma alone, the same error is a comma splice, which is the more common of the two and the one that catches people, because a comma feels like enough. There are three repairs, and every correct answer is one of them: a full stop and a capital, a semicolon, or a comma plus a coordinating conjunction (and, but, so, yet, for, or, nor). Adding a subordinating word such as because also works, because it turns one clause into a dependent one.
Taught in
Related terms
- comma splice — A comma splice joins two independent clauses with only a comma; a comma is not strong enough to hold two sentences together, so one of four repairs is needed.
- sentence fragment — A sentence fragment is a group of words punctuated as a sentence that lacks a subject, a verb or a complete thought.
- clause — A clause is a group of words with its own subject and verb; an independent clause can stand as a sentence, a dependent one cannot.
- semicolon — A semicolon joins two independent clauses without a conjunction, and separates list items that already contain commas.
Source: The grammar guide in this course, whose conventions follow the US Government Publishing Office's Style Manual for standard written American English, with standard grammar references for agreement, case, tense and sentence structure. The GPO manual is US federal government material, not subject to copyright in the United States. Every definition and example above was written for this course; no reference text is reproduced. (GPO Style Manual accessed 2026-10-27; definitions written 2026-10-27)