Run-on Sentences
While independent clauses — or clauses that could stand alone as complete sentences — cannot be joined only with a comma without creating an error (known as a comma splice), they must be joined with something. When two independent clauses are joined with nothing, this is called a run-on sentence. (Contrary to conventional wisdom, a run-on sentence doesn’t necessarily run on and on and on, though some do. A run-on sentence is a sentence-joining error. This is why the run-on sentence is also commonly known as a fused sentence.)
◊ I’ll meet you downtown at three o’clock I need you to help me pick out shoes.
The above sentence is incorrect because there is nothing joining “o’clock” and “I.” You could fix this probably in the same ways you fix comma splices:
1. Write two separate sentences, making sure that each is complete:
◊ I’ll meet you downtown at three o’clock. I need you to help me pick out shoes.
2. Join the two ideas with a semicolon if the ideas are closely related enough to belong in the same sentence.
◊ I’ll meet you downtown at three o’clock; I need you to help me pick out shoes.
3. Use a comma and a coordinating conjunction* to join the ideas.
◊ I’ll meet you downtown at three o’clock, and I need you to help me pick out shoes.
*Coordinating Conjunctions: FANBOYS, or
For
And
Nor
But
Or
Yet
So
4. Use a subordinating conjunction* to join the ideas.
◊ I’ll meet you downtown at three o’clock, since I need you to help me pick out shoes.
*Subordinating Conjunctions (some of them): after, although, as, as if, as though, because, before, even though, if, since, so that, though, unless, until, when, whenever, where, whereas, wherever, whether, while.