When people think of punctuation marks, it is usually the handy comma, the imperious colon, or the overly excited exclamation mark that comes to mind. The stodgy semicolon and sinuous question mark might get thrown into the mix, but rarely—if ever—will somebody mention a punctuation mark that, while omnipresent, often goes unnoticed. This is surprising considering that this punctuation mark is highly versatile and a favorite of skilled writers. It can add a spice—or a dash, if you will—to a sentence by adding emphasis to certain words and phrases.
I am talking about the em-dash, which looks like two hyphens connected into one long line. Depending on the sentence, the em-dash can have a similar function to parentheses, colons, commas, and even semicolons. But an em-dash is not the same as these other marks; it brings a different flavor to the sentence and adds a special emphasis that wasn’t there before.
To show how to wield this handy punctuation mark, I’ll start by comparing two sentences: one that contains an em-dash (or em-dashes) and one that contains another punctuation mark. I’ll begin with parentheses, then discuss commas, move on to a semicolon, and finally end with a colon.
Lastly, I’ll touch on how to avoid overusing or misusing the em-dash—which can become tempting once you learn its many uses.
1. Parentheses and the Em-dash
So, let’s start with parentheses versus em-dash, by comparing two sentences.
Dennis took his car (a tiny, two-door Honda) on a weekend road trip.
Dennis stuffed his four best friends into his car—a tiny, two-door Honda—for a weekend road trip.
In the first sentence, the fact that he has a small Honda doesn’t seem that closely connected to the fact that he took a road trip. Since we don’t want to bring too much attention to this information, we keep this information in parentheses. But in the second sentence, the size of the Honda is relevant to the road trip. Now he is “stuffing” four other friends into this small car. We use em-dashes to add emphasis to the size of the car.
It’s also important that when you set off a phrase using em-dashes that you used one em-dash immediately after the noun the phrase is describing and one immediately after the phrase. Don’t replace the second em-dash (as some tend to) with a comma or semicolon.
Identifying how an em-dash is used and actually using one in your own writing are two different things, the latter being trickier. Here’s a good strategy to use when trying to decide whether to use em-dashes or parentheses in your writing: If you find yourself wanting to throw in a little extra information about a noun in a particular sentence and are not sure whether the parentheses or the em-dash is the way to go, read the sentence out loud. When you get to the information contained between the em-dashes, add a little bit of humph as you enunciate each word. Then replace the em-dashes with parentheses and reread the sentence without adding any emphasis to the phrase in parentheses. In theory, that’s how your readers will interpret the sentence in their own minds—more emphasis, or “humph,” with the em-dash, and less with parentheses.
For instance, let’s say you are writing about a young pianist who mastered the works of composers known for their challenging pieces. You might want to highlight those names. The em-dash allows you to do this.
Mastering the works of her favorite composers—Rachmaninoff, Brahms, and Chopin—took many diligent years of practice.
If it sounds odd adding special emphasis to the composers when reading the sentence aloud, then parentheses are better.