Updated: Jan 30, 2021
What makes the em dash different from a hyphen or an en dash?
Em dashes are often used during an abrupt break in thought. If you read books — pretty much any books — you’ve seen them used in this instance before:
She nodded sharply, raising an invisible sword. “And damned be he—she—who cries, ‘Hold, enough!’” (Patricia Briggs)
The sentence would still be complete without the word(s) inside the em dash. That is what you want when you use the em dash this way. In this case, it’s similar to using parentheses. The em dash is used in this quote for emphasis. If the word she had parentheses around it, the sentence wouldn’t read the same, as there wouldn’t be enough emphasis on the word she.
Note that The AP Style Guide calls for leaving one space on each side of an em dash ( — ), whereas The Chicago Manual of Style (CMOS) calls for no space on either side of an em dash (—).
The AP Style Guide is used as a guideline for publications such as newspapers and magazines. The magazine publication that I work for follows AP Style for em dashes
( — ). When I edit fiction and nonfiction manuscripts, I follow CMOS guidelines of no space on either side of an em dash (—), if that is the writer’s preference.
The em dash is also used to indicate an interruption in dialogue. The example below is taken directly from CMOS, 17th Edition:
“Well, I don’t know,” I began tentatively. “I thought I might—”
“Might what?” she demanded.
See what happened there? The em dash was used to show that the first person speaking above was interrupted by an impatient person. (Em dashes are not used to show a speaker trailing off. Ellipses [. . .] are used for this purpose.)
“The em dash isn’t on my keyboard! Where do I find it?”
Here's what you can do to add an em dash to your text:
If you have a number pad on the right side of your keyboard, use ALT + 0151 to make the em dash appear. (Hold down the ALT button while entering 0151 and then release the keys.) Voila!
On a Mac, the keyboard shortcut Option + Shift + Dash (-) makes an em dash. Ta-da!
My laptop doesn’t have a number pad on the right side, so — before I was gifted a wireless keyboard and mouse — I let MS Word insert the em dash for me:
Simply write a word and type the dash/minus button twice (with no spaces in between) and then write another word after it and hit the spacebar. An em dash will automatically appear in place of the two dashes.
Yep! It’s that easy!
The em dash has other uses that I will not discuss here. If you want to learn all there is to know about em dashes, though, you can refer to CMOS, 17th Edition (Section 6.85).