Updated: Jul 17, 2020
Who knew that a horizontal line could be so versatile? Several different punctuation marks take that form: The hyphen, minus sign, and two different types of dashes (four types according to the Chicago Manual of Style). Even if no one has ever said that with great versatility comes great confusion, it is often true. In my experience as an editor, they are used by many writers interchangeably (Spoiler alert: They aren’t interchangeable). In this post, I will address the proper use of dashes.
An en dash is used with pairs of numbers or words to mean “to” or “through.”
An em dash sets off explanatory material in the same way as commas, parentheses, or a colon, but with more emphasis on the interruption.
What are the types of dashes?
The two types of dashes are the en dash and the em dash. Their names are derived from their width: They are, respectively, 1 en and 1 em wide. Em and en are standard typographical units. Traditionally, they were the width of a capital M and a capital N, but in modern typography, em is equal to the font size, and en is half of an em. If you really want to geek out, you can read about typography here. According to the APA publication manual, the en dash is also known as the midsized dash and the em dash can also be called a long dash. Wikipedia provides more interesting alternative labels: the en rule or the nut dash and the em rule or mutton dash. More important than the visual difference is the difference in how they are used. I like to the think of the en dash as connecting things, and the em dash as separating.
En dash usage
Use the en dash in place of “to” or “through” unless preceded by “from” or “between.” Here are some examples of en dash usage when expressing a numeric range:
The years 2002–2007
But: I was in graduate school from 2002 until 2007
The following are some examples of using the en dash to connect two places, directions, or times. The APA manual describes this usage as compound adjectives when the words are of equal weight.
The Boston–Chicago flight
An East–West journey.
The March–June reporting period
But: I drove from Boston to New York
The en dash is also used when expressing scores:
The Supreme Court voted 7–2 to overturn the ruling.
The Steelers beat the Ravens 24–0.
Or university campuses (if the institution styles it in that manner):
University of Wisconsin–Madison
The Chicago Manual of Style recommends using an en dash in place of a hyphen with compound adjectives if one or both of the parts have multiple words, but also recommends against such phrasing:
school-based learning (hyphen)
private school–based learning (en dash)
learning based in private schools (better)
Em dash usage
Em dashes are used to interrupt the flow of the text. Therefore, they should be used sparingly, particularly in academic writing. Em dashes are most often used in lieu of commas, colons, or parentheses to offset a clause or a phrase that amplifies, clarifies, or explains some other part of the sentence. Use the dash instead of one of those other types of punctuation when you want a little extra emphasis on the separation. Here are some examples of how to use an em dash.
Replacing a colon:
I spent the weekend doing something extraordinary—writing about dashes.
Mike—the best friend ever—is coming for a visit.
Three colleagues—John, Mary, and Sophia—are preparing the report.
Em dashes are a better choice than commas with for example and similar phrases:
I enjoy young adult fiction—for example, The Hunger Games—to more
Generally, punctuation adjacent to em dashes should be omitted, except that question marks and exclamation points can appear before a dash. The first of these three examples requires a comma to separate the independent clause from the dependent clause, but the comma is omitted in the second and third examples, each of which has a clause set off by em dashes. The final example includes an exclamation point:
Although I had eaten dinner, I was still hungry.
Although I had eaten dinner—it was very good—I was still hungry.
Although I had eaten dinner—it was amazing!—I was still hungry.
Do not use spaces before or after a dash:
incorrect: Word — Word
Unfortunately, you won't find a dash on your computer keyboard, but most word processing programs have a way to insert them. In Microsoft Word, the default autocorrect option for the en dash results in spaces on either side, so it is not ideal. Use the following keystrokes to insert an em dash:
Word1, two hyphens, Word 2, space (the two hyphens will autocorrect to an em dash)
Additionally, there are keyboard shortcuts available; however, PC shortcuts only work with certain hardware. Check the web for the options for your device and operating system. On a Mac, you can use these shortcuts, regardless of software:
Em Dash: Option+Shift+hyphen
En Dash: Option+Hyphen
Hyphens and dashes are not interchangeable. They vary in length (the hyphen being the shortest and the em dash being the longest) and in purpose. Use the en dash to express a numeric range, connect two words, or compare two numbers or words. Use the em dash to interrupt the flow of a sentence.
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