Comma Splice
Situations that may produce comma splices
- First clause is negative, second positive:
*Ginsberg is not a novel writer, he is a poet.
Ginsberg is not a novel writer; he is a poet.
- Second clause contains a conjunctive adverb such as however, therefore, or instead:
*She had intended to become a biologist, however, medicine seemed more exciting.
She had intended to become a biologist; however, medicine seemed more exciting.
- Words identifying the speaker divide a quotation between two complete sentences:
*"Medicine is a human frontier," Petric says, "The boundaries are unknown."
"Medicine is a human frontier," Petric says. "The boundaries are unknown."
Separate two main clauses with a comma only when they are joined by a coordinating conjunction
A comma cannot separate main clauses unless they are linked by a coordinating conjunction (and, but, or, nor, for, so, yet). Readers expect the same main clause to combine after a comma alone. When they find themselves reading a second main clause before they realize they have finished the first, they may have to reread. You have several options for revising comma splices.
Making seperate sentences
Revising a comma splice by making seperate sentences from the main clauses will always be correct. The period is not only correct but preferable when the ideas expressed in the two main clauses are only loosely related.
*Chemistry has contributed much to our understanding of foods, many foods such as wheat and beans can be produced in the laboratory.
Chemistry has contributed much to our understanding of foods. Many foods such as wheat and beans can be produced in the laboratory.
Making seperate sentences may be the best option if you are used to writing very long sentences in your native language and often write comma splices in English.
Inserting a coordinating conjunction
When the ideas in the main clauses are closely related and equally important, you may correct a comma splice by inserting the appropriate coordinating conjunction immediately after the comma to join the clauses.
*Some laboratory-grown foods taste good, they are nutritious.
Some laboratory-grown foods taste good, and they are nutritious.
Using a semicolon
If the relation between the ideas expressed in the main clauses is very close and obvious without a conjunction, you can separate the clauses with a semicolon.
*Good taste is rarae in laboratory-grown vegetables, they are usually bland.
Good taste is rare in laborator-grown vegetables; they are usually bland.
Subordinating one clause
When the idea in one clause is more important than in the other, you can express the less important idea in a phrase or subordinate clause. Subordination is often more effective than forming separate sentences because it defines the relation between the ideas more precisely.
*The vitamins are adequate, the flavour is deficient.
The vitamins are adequate. The flavour is deficient (revised).
Even though the vitamins are adequate, the flavour is deficient (improved).
more information on subordinating structures
Separate main clauses related by however, for example, and so on
Two kinds of words that are not conjunctions describe how one main clause relates to another:
- conjunctive adverbs, such as consequently, finally, hence, however, indeed, therefore, thus, ...
- other transitional expressions, such as even so, for example, in fact, of course, to the right, to this end, ...
When two main clauses are related by a conjunctive adverb or a transitional expression, they must be separated by a period or by a semicolon. The adverb or expression is also generally set off by a comma or commas.
*Most Americans refuse to give up their unhealthful habits, consequently their medical costs are higher than those of many other countries.
Most Americans refuse to give up their unhealthful habits. Consequently, their medical costs are higher than those of many other countries (revised).
Most Americans refuse to give up their unhealthful habits; consequently, their medical costs are higher than those of many other countries (revised).
Mind, conjunctive adverbs and transitional expressions are different from coordinating conjunctions (and, but, or, and so on) and subordinating conjunctions (although, because, since, and so on):
Unlinke conjunctions, conjunctive adverbs and transitional expressions do not join two clauses into a grammatical unit. They merely describe the way two clauses relate in meaning.
Unlinke conjunctions, conjunctive adverbs and transitional expressions can be moved within a clause. No matter where in the clause an adverb or expression falls, though, the clause must be separated from another main clause by a period or a semicolon.