The en dash and em dash are little bits of punctuation that look sort of like a hyphen. In fact, you've probably used a hyphen in places where an en or em dash should go. Feel guilty yet? Don't. Instead, feel proud that you're about to conquer the mystery of en dash vs. em dash for once and for all.
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En Dash vs. Em Dash
You know why you're here? You want to know the difference between an en dash and an em dash and how to use them. Oh yes, you do. Desktop publishing professionals know when to use an en dash vs. em dash, and this knowledge is a great way to impress a client.
Client: "What are these long lines separating thoughts here in this sentence? The Word doc I gave you had hyphens."
You (nonchalantly): "Oh, those kinds of breaks require a special punctuation mark called an em dash. So I put them in for you even though you didn't even know you needed them. I'm just that good."
Client: "Wow! Here, have a 10% bonus on this job for anticipating my needs. You rock!"
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All Right, What is the Difference Between an En Dash and an Em Dash, Smartypants?
Get this. They're based on typographical measurements. An em dash is the width of the size of the font. Wait, zuh? Try this: a 12-point font has an em dash 12 points wide. There are 72 points (approx.) to an inch, for reference. An en dash is half the width of an em dash.
Em dash: — (alt-shift-hyphen on Windows, option-shift-hyphen on Mac, — in HTML)
En dash: – (alt-hyphen on Windows, option-hyphen on Mac, – in HTML)
The en dash is generally used to indicate ranges of nearly anything, such as numbers, pages, dates, and game scores.
Right: Our team won the game 24–10. (en dash, because it's a game score)
Wrong: Our team won the game 24-10. (hyphen is wrong)
The contest runs July 7–21.
You can find the recipe on pages 74–76 of the cookbook.
The en dash is also used when phrases are hyphenated more than once (compounds of compounds). It's used so that the phrase looks better than if it had two hyphens, and helps make the compound phrase easier to read.
Example: Firefox is an open-source–based browser. (Notice that "based," the second word modified, is preceded by an en dash.)
Space is normally not added on either side of an en dash. Some typographers add hair spacing or track out spacing just a bit on either side (never to a full space width), but this is personal preference based on looks.
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When to Use an Em Dash
An em dash marks an interruption in a sentence, a change in direction. Usually two em dashes are used to mark the beginning and end of the interruption, though sometimes the sentence may end with the interrupting phrase.
Two em dashes:
The two leaders—one from Wyoming and one from Montana—sought to build support for the work of the commission.
The destruction—and there was no question the destruction was deliberate—horrified onlookers.
One em dash:
There was no way to the top of the mountain—or was there?
An em dash is also used in dialogue or fiction to indicate a statement being cut off.
Example: "We're safe here. The enemy can't possibly hit us at this dist–"
Space is traditionally not added on either side of an em dash. However, it's customary for typographers to track out a bit of space on either side of an em dash to give it room to breathe. Some add an entire space, but I think that looks a bit horse-y.
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So there you have it—some simple rules of thumb for handling the en dash vs. em dash question (see what I did there?). You see that they're really quite different from one another in usage, their only real commonality being that they look so similar! So put their looks behind you and bookmark this guide to remind you when to use each.
The Short and Long of It: When to Use Hyphens, En Dashes, and Em Dashes
How to use hyphens, en dashes, and em dashes? They're 3 different punctuation marks that only differ in their length from one another. Using them properly distinguishes the pro from the amateur. Read this series to learn when and why to use hyphens, en dashes, and em dashes.