Run-on sentences are independent clauses that have not been joined correctly. An independent clause is a word group that can stand alone as a sentence. (See 49a.) When two independent clauses appear in one sentence, they must be joined in one of these ways:

Recognizing run-on sentences

There are two types of run-on sentences. When a writer puts no mark of punctuation and no coordinating conjunction between independent clauses, the result is called a fused sentence.

A far more common type of run-on sentence is the comma splice—two or more independent clauses joined with a comma but without a coordinating conjunction. In some comma splices, the comma appears alone.

In other comma splices, the comma is accompanied by a joining word that is not a coordinating conjunction. There are only seven coordinating conjunctions in English: and, but, or, nor, for, so, and yet.

However is a transitional expression, not a coordinating conjunction, and cannot be used with only a comma to join two independent clauses (see 20b). For help recognizing run-on sentences, see the flowchart at the bottom of the page.

Revising run-on sentences

To revise a run-on sentence, you have four choices.

1. Use a comma and a coordinating conjunction (and, but, or, nor, for, so, yet).

2. Use a semicolon (or, if appropriate, a colon or a dash). A semicolon may be used alone; it can also be accompanied by a transitional expression.

3. Make the clauses into separate sentences.

4. Restructure the sentence; try subordinating a clause.

One of these revision techniques usually works better than the others for a particular sentence. The fourth technique, the one requiring the most extensive revision, is often the most effective.