hyphen (-)
A hyphen goes between words or syllables to link them together.
Example: Editors appreciate dash-savvy writers.
All English keyboards: the hyphen is the minus key next to zero.
en dash (–)
An en dash denotes a range between numbers or dates. It is so called because it is the same length as the letter “n.”
Example: The author used multiple dashes on pages 4–90.
Microsoft: alt + 0150
MS Word auto-format: enter [space], [hyphen], [space] between words.
Like this: word – word
Apple: option + hyphen
Smartphone or tablet: hold down the hyphen key until more options appear. The N-dash is probably the middle choice.
em dash (—)
An em dash denotes an interruption. It is so called because it is the same length as the letter “m.”
Example: Authors—even professional ones—often use dashes incorrectly.
Microsoft: alt + 0151
MS Word auto-format: enter [hyphen][hyphen] between words without spaces.
Like this: word–word
Apple: shift + option + hyphen
Smartphone or tablet: hold down the hyphen key until more options appear. The M-dash is the widest choice.
Lara Willard 
Great post, Lara!
I recently saw this dash-related sentence in a tabloid mag:
“Ever since George’s birth, William and Kate have been inundated with warm wishes and gifts for their son ndash; especially when the trio were on their royal tour in April, visiting Australia and New Zealand.”
All hail Prince Ndash! 🙂
Bahahaha. Oh dear.
Thank you Lara! That’s useful.
One tip for Scrivener users: if you can’t get the en and em dashes to look different, check which font you’re using. I was puzzled for a minute because they looked identical, but then I realised I was typing in Courier. Cochin works fine.
Good point! Courier is a monospace font, so every character has the same width, even m’s and n’s, and therefore en dashes and em dashes 🙂
I’m part of a team collaborating on a manual. Some of us use MAC and others use PC. When we go back and forth, the dashes revert to double hyphens. Is there a universal way to do the em-dash?
Very strange! If someone does Alt+0151 on the PC and option+shift+minus on the Mac, both should create the em-dash. The only reason I can think that it might switch would be if they were typed with the auto-format and not manually inserted. You could copy an em-dash from online and paste it in using the find and replace.