Another type of run-on sentence is called the fused sentence. A fused sentence contains two or more independent clauses that run together, with no punctuation or subordinate conjunctions separating the clauses. A fused sentence is often more difficult to correct compared to a comma splice, as it is even trickier to figure out where the first clause ends, and where the second one begins.
Below is an example of a fused sentence, and how to correct it with the addition of appropriate punctuation, as well as some rephrasing:
Incorrect: In his haste to leave the house for school Dylan accidentally took his sister’s bag looking for his science assignment to submit to the teacher he was surprised to find that the bag only contained Primary 2 worksheets and colour pencils instead of his own books and stationery.
Correct: In his haste to leave the house for school, Dylan accidentally took his sister’s bag. While he was looking for his science assignment to submit to the teacher, he was surprised to find that the bag only contained Primary 2 worksheets and colour pencils, instead of his own books and stationery.
In the example above, a period is added to separate the clause on Dylan accidentally taking his sister’s bag and the following clause on his looking for his science assignment – this is done because the first clause can stand on its own without being followed by another clause.
In addition to simply adding conjunction words or punctuation to correct the example of the run-on sentence above (as would be the case for a comma splice), the student may also need to do some rephrasing to make a fused sentence grammatically correct. In this case, the phrase “While he was” is added to the second clause on Dylan looking for his science assignment, to make this clause stand independently on its own.
When in doubt as to whether a sentence is run-on, it is best to keep writing simple sentences that have a clear subject, verb, and object relationship. While it is still possible for long, complex sentences to be grammatically correct, it is safer to stick to writing short-but-grammatically-correct sentences first, until one is certain that the long sentences they write are no longer run-on.