Type option + shift + hyphen on your Mac keyboard and you get the mighty em-dash—the long dash, the pause that refreshes, the needle that injects a booster shot of information into a sentence.
Used either singly or in pairs, the em-dash is a multicolored character that can play the role of a comma, a colon, a semi-colon, or parentheses.
Consider this simple sentence:
She had finally won the prize, a gold medal.
The comma is just fine. But try an em-dash instead:
She had finally won the prize—a gold medal.
Same meaning, same grammatical soundness. But the em-dash forces a more pronounced pause, shining a light on that gold medal—without resorting to the nuclear option of an exclamation point.
A colon would have much the same effect:
She had finally won the prize: a gold medal.
But the colon seems somewhat formal, does it not? In non-academic writing, the em-dash feels more at home.
Working in pairs, the first em-dash interrupts the flow of a sentence so that related information can be added, and the second em-dash returns the reader to the main sentence for its conclusion.
Commas can perform this function, but only if the additional information is short and simple and contains no commas of its own. Otherwise, you’d end up with:
By the time they reached the remote cabin, exhausted, thirsty, confused by the sudden turn of events, and now without their guide, it had already started to snow.
Not bad. But with em-dashes to set off the extra words and phrases, the whole sentence becomes clearer and more powerful:
By the time they reached the remote cabin—exhausted, thirsty, confused by the sudden turn of events, and now without their guide—it had already started to snow.
When the additional wording is more factual or explanatory, parentheses can handle the job:
With his family wealth and name recognition (his father is a former governor, his brother a state senator), he was the front-runner the moment he entered the race.
But some consider parentheses, like the colon, too formal for non-academic writing. (We prefer to reserve them for author’s asides.) Em-dashes, do your thing:
With his family wealth and name recognition—his father is a former governor, his brother a state senator—he was the front-runner the moment he entered the race.
So the em-dash can add a dramatic pause, or allow you to add extra information to a sentence. Very useful—so be careful not to rely on it too often. Overuse of the em-dash results in overstuffed, scatterbrained, or simply unpolished writing. (Unless, of course, it’s being done purposefully for that effect.)
A single em-dash is strong; a pair is powerful. But three’s a crowd.
If you’re thinking of using more than a pair of em-dashes in a single sentence, don’t—you’re trying to cram too much information into one sentence. (There was the em-dash acting as a semi-colon.) Even using two single em-dashes in the same paragraph is less than desirable.
So, now that you’re better acquainted with the em-dash (and the en-dash), you never again have to call a hyphen a “dash.” Thank you.