A semicolon is, in some ways, a super comma. Unlike the comma, however, you must have two independent clauses. What is this bit about clauses? A clause, to put it simply, is a sentence that contains a subject and a verb. An independent clause is a sentence that is a complete thought. A dependent clause is one that does not complete a thought and requires additional information to do so. Example:
Fighting in the old restaurant = DependentNotice the difference?
They were fighting in the old restaurant = Independent
Now, in regards to semicolons, you need two independent clauses. You can't say:
She was a happy girl; smiling all the time.
That makes no sense because the first part is independent, but the second is dependent. It requires additional information to make it a complete sentence. The following would be correct:
She was a happy girl; she smiled all the time.Two complete clauses (sentences). Generally speaking you always want the two clauses around the semicolon to be related. Notice how the above example has a happy girl who smiles. Both are related to her happiness. Sometimes you can get away with it, but for the most part you should stick to having the sentences stick together. Besides, if you have a sentence that is unrelated it probably should be on its own somewhere anymore.
Just remember this the next time you want to use the semicolon. It can be your friend if you use it correctly; it can also be your greatest enemy. If you use it poorly it is a sure fire way to end up in that slush pile or in the garbage can. Editors generally do not like flashy punctuation; semicolons can be seen this way if you use them a lot. It's a clear warning when your use of the semicolon is incorrect that you are not developed enough in your writing for publication. I personally love the semicolon. It's a cool piece of punctuation I think.
So, that's that!
So, that's that!