Last week I started a short punctuation series on semicolons, colons, and dashes. I had said it was going to be a two-part series, but I was only kidding myself. Once a person starts talking about colons and dashes, it's hard to stop. So we find ourselves not at the end of a two-part series, but spang in the middle of a three-part series: colons today, dashes next week.

By way of review, the semicolon is not a very flexible punctuation mark (though I have lots of students who find very creative uses for the semicolon). A semicolon can be used to separate items in a complex series (that is, lists in which one or more items includes a comma) or it can be used to join two independent clauses into a compound sentence. That's it: any other use of the semicolon constitutes a punctuation error.

Colons and dashes, on the other hand, are both a little more flexible than semicolons. For the purposes of this letter, I am going to stick to the uses of the colon within prose sentences and skip the many specialized uses in business memos, titles, bibliographical citations, scriptural citations, etc.

In preparing for this letter, I ran across a summary of the colon that I found very helpful: a colon signifies expectation or addition. In every proper use of the colon, you are adding something to a sentence that is already (grammatically) complete without it. The colon, then, either sets up an expectation that is fulfilled by the information after the colon, or it signals that you are about to give the reader bonus information that will add to his or her understanding of what you just said.

A Habit reader recently asked about the use of semicolons, colons, and dashes. These punctuation marks can be exceedingly helpful for expressing nuance in your prose. But if you misuse them, bad things can start happening to good people. Nuance is a delicate flower; it wilts in the presence of faulty punctuation. This week's issue of The Habit is the first of a two-part series on the effective use of these three punctuation marks. We'll talk about semicolons today and colons and dashes next week.

The semicolon is not an especially flexible punctuation mark. In fact, it only does two things:

1.A semicolon separates items in a series IF at least one item in the series contains a comma.
This is sometimes called the "complex series" use of the semicolon.  

2.A semicolon joins two independent clauses into a compound sentence.
An independent clause is simply a clause (that is, a string of words containing a subject and a verb) that can stand on its own as a sentence.