A run-on sentence contains two or more independent clauses that appear together without appropriate punctuation between them. A run-on sentence is sometimes called a fused sentence.
Run-on sentences are not necessarily long sentences. They are usually confusing for the reader because they try to convey multiple concepts without making clear connections. To correct a run-on sentence, writers can split it into two simple sentences by putting a period at the end of the first subject-verb clause and capitalizing the first letter of the second subject-verb group.
When two sentences are so closely related in meaning that a period would put an abrupt end to the first sentence, writers can use a semicolon to divide the sentences. Alternatively, writers can insert a comma and coordinating conjunction to join the two independent clauses together into a grammatically correct sentence. Coordinating conjunctions include "and," "or" and "so."
Another way to fix a run-on sentence is to place a subordinate conjunction before one of the independent clauses, making it a complex sentence. Writers can also correct long run-on sentences by splitting the ideas into three independent clauses and inserting a comma and coordinating conjunction after the first two. Readers can identify run-on sentences by turning the sentence into a yes-or-no question. Run-on sentences have more than one complete thought and do not pass the test.