The Writing Center @ The University of Wisconsin - Madison
The Writer's Handbook
An Editing Checklist

9. Comma splices

Do not link two independent clauses with a comma (unless you also use a coordinating conjunction: and, or, but, for, nor, so, yet).

Instead use a period or semicolon, or rewrite the sentence.

Comma splice:

In 1952 Japan's gross national product was one third that of France, by the late 1970s it was larger than the GNPs of France and Britain combined.

Correct:

In 1952 Japan's gross national product was one third that of France. By the late 1970s it was larger than the GNPs of France and Britain combined.

Comma splice:

Diseased coronary arteries are often surgically bypassed, however half of all bypass grafts fail within ten years.

Correct:

Diseased coronary arteries are often surgically bypassed; however, half of all bypass grafts fail within ten years.

For more information on commas see Commas: Punctuating Restrictive and Non-restrictive Modifiers and Punctuating Coordinating Conjunctions and Sentence Adverbs, or take one of the free grammar, style, and style classes offered by the Writing Center.