• Separates an inserted thought or clause from the main clause, such as:

“I can’t believe how pedantic Ken is about writing—doesn’t he have anything better to do?”

“Hunter strode into the room—was he mad?—and the family stopped and stared.”

“Computers make everyday punctuation—for reasons that we’ll discuss later—more precise yet more confusing.”

• Shows when dialogue has been interrupted:

“I reached in and pulled the spray can out of my backpack—” “In front of the police?”

Extra:

Here’s another obscure, old-fashioned use for the m-dash: When letters are uncertain or missing from a word that you are quoting or reporting about, you insert two m-dashes where the unknown letters would be.  For example:

“Using dashes is a bit of an ad——n [addiction?]”, said Jennifer.

Break the rules!

If you are writing formal documents or writing for publication, it’s best to use dashes correctly.

However…  Some people prefer the way a ‘space-en-dash-space’ looks. Sometimes when you use the em-dash people say, “What is that? I don’t like that big long dash thing.” Some technical writers think the n-dash is the only one to use.

It’s not a big deal. I usually use ‘space-n-dash-space’ instead of the m-dash – just to keep everyone happy.  You can see this ‘wrong-n’ method used in countless websites, magazines and papers as a replacement for the m-dash.  If you use the ‘wrong-n’ method and use it consistently, it works fine and seems to keep the greatest number of people happy.

How to type the endash and emdash in Microsoft Word

Endash:
Automatically created in Word when you type “something – something” (word-space-hyphen-space-word).

Emdash:
Automatically created in Word when you type “something–something” (word-hyphen-hyphen-word).

Take full control of your dashes in Microsoft Word!

Can I use the en-dash or em-dash in Twitter or Facebook?

[updated]

[New: how to type the n-dash on a phone or tablet]

Yes! With a simple trick for touchscreen keyboards, it’s easy to use the n-dash and m-dash on a phone or tablet.^[1]