{{anchor|Run-on sentences}}<!--Stop turning the description of run-on sentences into a run-on sentence. That's not funny anymore.-->
A run-on sentence is a [[sentence (linguistics)|sentence]] that consists of two or more [[independent clauses]] (i.e. clauses that have not been made dependent through the use of a relative pronoun or a subordinating conjunction) that are joined without appropriate punctuation: the clauses "run on" into confusion. The independent clauses can be "fused", as in "It is nearly half past five we cannot reach town before dark", in which case the two independent clauses might be separated (between "five" and "we") with a period [...five. We...], a comma and conjunction (...five, and we...), or a semicolon (...five; we...). The independent clauses can be joined ''inadequately'' with only a comma (the [[comma splice]]).
In general, run-on sentences occur when two or more independent clauses are joined without using a [[Grammatical conjunction|coordinating conjunction]] (iei.e. ''for'', ''and'', ''nor'', ''but'', ''or'', ''yet'', ''so'') or correct punctuation (iei.e. semicolon, dash, or period).\<ref name="Fused">{{cite web |last1=Berry |first1=Chris |last2=Brizee |first2=Allen |title=Runons – Comma Splices Fused Sentences |date=2006-08-31 |url=http://owl.english.purdue.edu/owl/resource/598/02/ |access-date=2008-01-24|archive-url=https://web.archive.org/web/20180612163000/https://owl.english.purdue.edu/owl/resource/598/02/|archive-date=June 12, 2018|url-status=dead}}</ref><ref name="CCC">{{cite web |title=Run-on Sentences, Comma Splices |url=http://grammar.ccc.commnet.edu/grammar/runons.htm |access-date=2008-01-24}}</ref><ref>{{cite news |url=https://www.elc.edu/english-grammar-lesson-run-ons/ |title=English Grammar Lesson - Run-Ons! - ELC |date=2017-05-19 |work=ELC - English Language Center |access-date=2017-09-14 |language=en-US}}</ref> A run-on sentence can be as short as four words – for instance, ''I drive she walks'', or even ''I drive, she walks,'' – because in these short cases there are two [[Grammatical subject|subjects]] paired with two [[intransitive verb]]s. An [[imperative sentence]] like "Run walk" can be a run-on even if it only has two words.
While some sources view comma splices as a form of run-on sentences,<ref name="CCC">{{citeweb |title=Run-on Sentences, Comma Splices |url=http://grammar.ccc.commnet.edu/grammar/runons.htm |access-date=2008-01-24}}</ref> others limit the term to independent clauses that are joined without punctuation.<ref name="Fused">{{cite web|last1=Berry |first1=Chris |last2=Brizee |first2=Allen |date=2006-08-31 |title=Runons – Comma Splices Fused Sentences |url=http://owl.english.purdue.edu/owl/resource/598/02/ |url-status=dead |archive-url=https://web.archive.org/web/20180612163000/https://owl.english.purdue.edu/owl/resource/598/02/ |archive-date=June 12, 2018 |access-date=2008-01-24}}</ref><ref>{{cite book |last1=Hairston |first1=Maxine |last2=Ruszkiewicz |first2=John J |last3=Friend |first3=Christy |title=The Scott Foresman Handbook for Writers |url=https://archive.org/details/scottforesmanhan00hair_0 |url-access=registration |edition=5th |publisher=Longman |year=1998 |location=New York |page=[https://archive.org/details/scottforesmanhan00hair_0/page/509 509]|isbn=9780321002488 }}</ref>
Per ''[[The American Heritage Dictionary of the English Language]]'', the term "run-on sentence" is also used for "a very long sentence, especially one lacking order or coherence".<ref>[https://www.ahdictionary.com/word/search.html?q=run-on%20sentence ''The American Heritage Dictionary of the English Language'']</ref>