Just as roadway signs help drivers find their way, punctuation marks guide readers.
Both types of guideposts have specific functions, as well.
Tailgating the previous Brighter Writer column, which was brimming with bad-driving analogies, let’s consider how those little dots, curves and line segments on the page help your readers navigate their way to your message:
A period at the end of a sentence is a stop sign. Period.
Commas are like the ubiquitous yellow signs offering any of a number of advisories—such as a curve left or right, an intersection (and its configuration), two-way traffic, or a pedestrian crossing. Likewise, the comma has myriad uses: in series, nouns of direct address, appositives and so on. They are elaborated upon here.
A colon, like a “Speed Zone Ahead” sign, heralds something imminent that warrants the reader’s attention: a list or a lengthy quote or excerpt.
A semicolon is like an “Alternate Merge” sign, directing traffic and making clear who goes next. The semicolon performs two functions: It connects two short sentences, and it organizes complex series.
In the former, there’s no need for a conjunction such as and or but; the semicolon has that covered.
In the latter, a semicolon wrangles, prioritizes and orders similar elements into subgroups; segments the disparate subgroups by format, type or genre; and keeps the whole mess clear for editors, readers and other content consumers.
An ellipsis is akin to a “Detour” sign. It should be used to indicate an interruption of quoted matter or of an excerpt from some published matter, such as this:
“We the People of the United States … do ordain and establish this Constitution for the United States of America.”
A full 34 words have been excised from the above. The ellipsis provides a bit of a shortcut. By the way, it’s best not to use an ellipsis, with its very specific purpose, in lieu of an em dash.
Em dashes and parentheses are like the orange signs marking a work zone, advising one to proceed slowly for a while. These two punctuation pillars perform roughly the same function—setting apart significant but nonessential information—but they vary slightly in their respective applications. (See these examples?)
Parentheses, like quotation marks, travel exclusively in pairs. More than one pair (such as this set and the next) can appear within a single sentence (without causing confusion).
Em dashes occasionally fly solo—as is the case in this sentence. The “two’s company, but three’s a crowd” rule applies with em dashes, though. Because they don’t have open and closed versions—as parentheses and quotation marks do—it’s best to avoid having more than two—or your reader can get confused. (See what I mean?)
An exclamation point correlates to the sirens and flashing lights of an emergency vehicle. Use it only when absolutely necessary. (It usually isn’t.) If you think you need one to give readers a jolt, you’re better off conjuring a stronger verb, a pithier phrase or more vivid imagery.
The question mark doesn’t really have a road sign counterpart. Rather its equivalent is a response to the random, reckless behavior of your fellow motorists, prompting you to wonder: Why would you even imagine making a left turn from the right-hand lane, you troglodyte?