An em dash (
—) is slightly longer than an en dash (
–) and both are longer than the hyphen or minus symbol (
-). Typically the em dash is used like a comma or parenthesis—to denote a break in a sentence—though the en dash is often seen being used in this manner as well. When used in this way the en dash should get surrounded by spaces while the em dash should not. However only the en dash should be used when defining a span or range, such as 1985–2014 or pages 53–102. The em dash is also used when citing a quote like:
"The secret of getting ahead is getting started." — Mark Twain
On a Mac the em dash can be typed with
alt + shift + minus and the en dash with just
alt + minus.