This is something I've been confused about for some time. Well, not confused, exactly. I'm very clear on the rules I was taught, but I've been told more than once that those rules are wrong.
I've tried doing research on the net, but, as usual with grammatical rules, it's hard to get a single clear answer.
Many sources seem to indicate that what makes a sentence a run-on is improper usage of a conjunction. That if you string together two or more independant clauses (things which could serve as complete and independant sentences)
without using a conjunction (or using a conjunction improperly), then you have a run-on.
Example: I went to the car I opened the door.
Solution: Add something after "car." A period, a semicolon, or a comma and the word "and" would serve.
The solution (and the need for it) is obvious to me, but it's not what I'd call a run-on sentence.
I was taught that a run-on happens when you string together three or more independant clauses
with two or more conjunctions.
Example: I came,
and I saw,
and I conquered.
To me, that's a run-on sentence. Possible solutions would be to seperate the clauses into two or three sentences ("I came. I saw. I conquered."or "I came, and I saw. I conquered.") or to convert the entire thing into a list ("I came, I saw, and I conquered.").
(Note, BTW, that the way I was taught, a semicolon serves the same function as the comma-and combination. Therefore, "I came; I saw; I conquered." or "I came, and I saw; I conquered." would also be considered run-ons.)
I've been told that this is unusual, to say the least. That, in fact, the sentence is fine as it is. That, basically, my teacher was a lone nutcase, and I should unlearn this rule.
I have found some evidence that, at the least, my teacher was not alone. Wikipedia's article on compound sentences (
click here and then select the link entitled "Compound Sentence (Linguistics); the boards won't allow me to post a link which contains parentheses) has the following to offer:
Run-on sentences
It is common for manuals of style, grade school English teachers, and other such proponents of prescriptive grammar to caution against the use of run-on sentences, defined as a compound sentence with "too many" independent clauses. While the exact specification of "too many" is obviously subjective, a commonly given number is three.
Examples:
Bob gave me a book and I read it and I didn't like it and I gave it back to him.
Grandma came to visit and we went to the zoo and we saw the ferrets and my friend Emily has a ferret.
It can be argued, however, that at least when teaching children, this advice against run-on sentences is not entirely a prescription on their grammar but rather a way of teaching that clauses in a sentence should be semantically related, not just a stream of consciousness. Therefore, although both examples above have the same number of independent clauses, it is probably the second that should be singled out as a run-on.
Note that the term run-on sentence is not usually used for complex sentences with large number of clauses. For example,
Bob gave me a book, which I read and I didn't like, so I gave it back to him.
is not a run-on sentence.
That is what I was taught (I'm not alone!!), but I'm still confused about how correct it is.
So, all you FoLC grammarians... Have at it!
Paul