Comma Splice (Run-On Sentence)

The comma splice is probably the single most common punctuation error that I see in the writing assignments for this class. A comma splice happens when you try to use a comma to coordinate two independent clauses:

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

Do you see the two independent clauses? They are statements that can stand on their own as complete sentences:

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

You cannot use a comma to coordinate two independent clauses. Luckily, there are many possible solutions to this punctuation problem.

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. If you tried to join them with a comma to begin with, then you probably see some kind of close connection between the statements. Read on for ways to fix a comma splice that can express a relationship between the two statements.

SEMICOLON. One way to express the close connection between the two statements is to join them with a semicolon.

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

For more information, see this page: Semicolons.

COORDINATING CONJUNCTION. You might be able to join the two statements with a 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.

For more information, see this page: Coordinating Conjunctions.

SUBORDINATING CONJUNCTION. A subordinating conjunction is the strongest way to express a relationship between the two statements. For example, if you think about the relationship between these two statements, you might detect a causal relationship, answering this question: Why did Robin Hood live in the forest?

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

If the subordinate clause ("because...") comes at the end of the sentence, no comma is needed. If you put the subordinate clause first, you need a comma. For more information, see this page: Subordinating Conjunctions.

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

(Source: BBC's Robin Hood)

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