Advanced Business Writing
Punctuation and Grammar

Dashes

Using horizontal lines, short and long, is acceptable punctuation. The hyphen is a short dash; the en dash is the width of the capital letter N; and the em dash is the width of the capital letter M. When you hear people talk about using a dash, they are usually talking about the em dash (sometimes written m-dash).

These lines are commonly used without spaces on either side of them:

While relaxing in the self-service cafeteria, I did not hear the announcement for my Omaha–Dallas flight. I begged the ticket agent—to no avail—for a seat on the next flight.

The hyphen is used to make compound words (long-term) and to create prefixes to keep things clear (all-encompassing). Because the hyphen is easy to type, and because the em dash is not as easy to type, people too often use the hyphen in place of the em dash:

The ticket agent checked my carry-on bag - as we were boarding - because he said it was too heavy for the overhead bins.
[bad]

That makes your writing look like you typed it on your grandfather's PC (or your great-grandfather's typewriter).

The ticket agent checked my carry-on bag—as we were boarding—because he said it was too heavy for the overhead bins.
[better]

The en dash forms the equivalent of the words to or through:

In the August–October issue of the airline magazine, pages 15–21 featured an article on the 2016–2017 season for the Stanley Cup champions.

If you introduce a time span with a word such as from or between, do not use the en dash:

She served as the airline CEO from 2009–2014.
[bad]

She served as the airline CEO from 2009 to 2014.
[good]

The em dash is an attention-getter. It can be used to interrupt, isolate, highlight, emphasize, or simply pause. It can replace italics as well as the colon. And it can relieve some of the boredom from slogging through dense paragraphs of text.

One problem with using the em dash is how easily it can lull you into losing track of proper grammar:

The beverage cart arrived late—an occurrence I expect when sitting in the back row—I have learned to bring my own drink.
[huh?]

Cover up the words inside the double dashes, and see if what remains is both correct and coherent:

The beverage cart arrived late I have learned to bring my own drink.
[bad]

An easy fix here is to add a conjunction after the second em dash:

The beverage cart arrived late—an occurrence I expect when sitting in the back row—but I have learned to bring my own drink.
[good]

Another problem with using the em dash is when you use several of them in different ways within a sentence:

Just after the plane took off—it had been on the tarmac for two hours—I realized I had forgotten to pack my umbrella—something I usually need in Seattle.
[bad]

Here the coordinated dashes were used to isolate an explanation and the single dash was used to set off a comment. Avoid doing that. It confuses.

The em dash conveys horizontal movement to the eyes, which stimulates the brain. That's a good thing. Yes, it can be overused—but it takes a lot to do that. Most people writing at work could improve their prose with more frequent use of the em dash. How frequent is too frequent? When they become more of a disruption than a guide. Most people are okay with one em dash per paragraph. You should have a good reason for using more than that.

Lesson: Dashes
Module: Punctuation and Grammar
Course: Advanced Business Writing