The Fused Sentence
Recognize a fused sentence when you see one.
A fused sentence, also called a run-on, occurs when a writer has connected two main clauses with no punctuation. A main clause makes a complete thought, so you should not find two of them smashed together in a single sentence.
The pattern looks like this:
main clause + Ø + main clause.
Here is an example:
Driving home from school, Brett vowed to protect the fragile ecosystem all the while the tires of his Cadillac Escalade flattened the toads hopping on the wet streets.
The first main clause is Brett vowed to protect the fragile ecosystem, and the second is the tires of his Cadillac Escalade flattened the toads hopping on the wet streets. Notice that the two clauses run together with no punctuation.
Fixing a fused sentence is easy. All you have to do is pick one of the four available strategies.
First, you can break the error into two separate sentences, like this:
Driving home from school, Brett vowed to protect the fragile ecosystem. All the while, the tires of his Cadillac Escalade flattened the toads hopping on the wet streets.
Another good option is to connect the two main clauses with a comma and a coordinating conjunction:
Driving home from school, Brett vowed to protect the fragile ecosystem, yet all the while, the tires of his Cadillac Escalade flattened the toads hopping on the wet streets.
You can also use a semicolon, a mark of punctuation as strong as a period:
Driving home from school, Brett vowed to protect the fragile ecosystem; all the while, the tires of his Cadillac Escalade flattened the toads hopping on the wet streets.
Your last option is to use a subordinate conjunction. This method reduces one of the two clauses to an incomplete thought:
Driving home from school, Brett vowed to protect the fragile ecosystem as the tires of his Cadillac Escalade flattened the toads hopping on the wet streets.