Comma, Semicolon and Colon

Punctuation Pointers

Judging by the errors I encounter, punctuation confuses many people. But once you know a few rules, it's easy to get it right. The following advice will help you avoid the most common mistakes.

• With the comma, the most frequent error is that of omission: Fred picked up a case of beer then drove to the golf course. To indicate a pause, a comma should follow beer.

Tip: Read your draft aloud. Wherever you pause naturally, a comma is probably needed.

A more controversial question is whether to use the "serial comma," the final one in a series. Which is correct? (a) You obtain health benefits from apples, pears and oranges. Or (b) You obtain health benefits from apples, pears, and oranges.

Neither is wrong. It's simply a matter of style. You may use either with impunity, so long as you are consistent within a document. But I favor the serial comma. It looks better. And it can prevent ambiguity, as this amusing example demonstrates: Indicate your name, address, sex and housing requirements.

• The semicolon may be the most misunderstood punctuation mark. It's used to divide phrases within a sentence, each of which could be a complete sentence: Please excuse the delay; I had a deadline. The only other, and far less common, use for the semicolon is where a lengthy series of phrases contains internal commas. To preclude confusion, semicolons separate each phrase.
• The colon is an introductory device. He spent his vacation reading his three favorite authors: Dickens, Proust, and Grisham. A good rule of thumb is to use a colon only if the words "that is" would make sense in its place.