Semicolons: Don’t let rules-lawyers intimidate you into avoiding semicolons; they are just as acceptable and useful as commas and periods. A semicolon changes the sentence’s tone and tempo, just like changing the order of the words. It’s not right or wrong–it’s a style choice.
Many people have a hard time grasping the use of this mark. Here is my attempt to make it simple:
The most common use of semicolons is to combine two related sentences into one, to emphasize their strong connection. The semicolon replaces and, so, because, and similar conjunctions.
In the following examples, any of the three versions are acceptable. Your choice depends upon the mood of the passage.
You should wear red. It looks good on you. <-> You should wear red because it looks good on you. <-> You should wear red; it looks good on you.
We made a lot of money. We bought a lot of nice things. <-> We made a lot of money, so we bought a lot of nice things. <-> We made a lot of money; we bought a lot of nice things.
Important: The two clauses must be closely related ideas. They must have their own subjects and verbs and be able to stand alone as separate sentences without any rewording.
The semicolon has other uses, but this one is the most important. If you know this usage, you will be able to use the semicolon without overusing it. The mark’s other use is as a replacement, in very specific circumstances, for the comma. If you wrongly omit a semicolon in those spots, it’s no big deal; your proofreader will easily catch it.
When you’re ready to learn the semicolon’s other technical uses, The Chicago Manual of Style‘s passage about it is surprisingly clear, especially in the less-bloated (and cheaper) earlier editions. Even better is The Bedford Handbook, by Diana Hacker. Editors need Chicago, but for working writers, Bedford, with its copious usage examples, is a friendlier resource. You can pick up a used 7th edition online for pennies plus shipping.