Comma Splice (Run-On Sentence)

A run-on sentence is when you have two (or more) independent clauses that are run together in a single sentence. You can use conjunctions to coordinate the clauses (see below) or you can use some creative punctuation (again, see below) — but you cannot just use a comma. A comma is not enough to join two independent clauses into a single sentence. When you try to use a comma to coordinate two independent clauses, the result is called a "comma splice" because the comma is being used to splice the two clauses together, and that is a task that the poor old comma cannot handle.

This sentence, for example, is a comma splice:

Robin Hood lived in Sherwood Forest, he was an outlaw.

Do you see the two independent clauses? Independent clauses are statements that can stand on their own as complete sentences, having both a subject and a verb:

• Robin Hood lived in Sherwood Forest.
• He was an outlaw.

So, once you have found a comma splice, what to do? You have lots of options, and you'll want to choose the option that gets your meaning across to your readers.

SEPARATE SENTENCES. You can break the run-on sentence up into two separate sentences.

• Robin Hood lived in Sherwood Forest. He was an outlaw.

This is not the most elegant solution, but it does work.

A better solution, however, is to find a way to express the close connection between the two sentences verbally. You can express the connection with a conjunction, either a coordinating conjunction like "and," "but," or "or" (putting the two statements on an equal level to each other) or a subordinating conjunction (which makes one statement into the main clause, while the other clause is secondary to it).

COORDINATING CONJUNCTION. When you join two independent clauses with a coordinating conjunction, you need to use a comma before the conjunction:

• Robin Hood lived in Sherwood Forest, and he was an outlaw.
• Robin Hood was an outlaw, but he stole only from the rich and gave to the poor.
• You might have heard the story of how Robin Hood first met Little John, or perhaps that story is new to you.

For more information, see this page: Coordinating Conjunctions.

SUBORDINATING CONJUNCTION. When you use a subordinating conjunction, you have to decide which is the main clause and which is the subordinate clause.

The main clause does not have to come first, as you can see by comparing the two sentences below. In the first sentence, the main clause comes first, but in the second example the subordinate clause comes first and is separated from the main clause by a comma:

• Robin Hood lived in Sherwood Forest because he was an outlaw.
• Because he was an outlaw, Robin Hood lived in Sherwood Forest.

For more information, see this page: Subordinating Conjunctions.

SEMICOLON. Finally, another way to express the close connection between two statements is to join them with a semicolon. Unlike a comma, a semicolon does indeed have the power to coordinate two independent clauses:

• Robin Hood lived in Sherwood Forest; he was an outlaw.

For more information about the use of the semicolon, see this page: Semicolons.

Comma splices and other kinds of run-on sentences are probably the single most common type of writing error that I see in the Storybooks. I hope these notes can help you to find and fix the comma splices in your own writing. If you have ideas about how I can improve the information provided here, please let me know!

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Because he was an outlaw, Robin Hood lived in Sherwood Forest.

(Source: BBC's Robin Hood)

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