August 15, 2013Grammar, Usage, and Punctuation
Em-dashes are the longest of the three short-horizontal-line punctuation marks.
the hyphen -
the en-dash –
the em-dash —
Em-dashes are used—and mostly underused—to mark parenthetical remarks. Much legal prose would improve by having some commas, and almost all parentheses in the text, replaced by em-dashes.
Don’t use two hyphens to create an em-dash; that’s an unhandy relic of the typewriter era.
Typographers argue about whether an em-dash should be set off on either side with a small space (smaller than a regular space), or—as you see them here—unspaced. Unless you know how to insert half-spaces or ¼ em-spaces in Word, don’t worry about this issue, but also don’t hit the space bar before and after your em-dashes.
If you want an em-dash in Word, you can pick it from a dropdown symbol picker, or type Ctrl-Alt-NumLock-[dash] (where [dash] is the one on the number pad, not the one above and to the right of the P key).
Em- and en-dashes are named because of the historical typesetting custom that an en-dash was the width of a lowercase “n” and the em-dash the width of a lowercase “m.” They aren’t always those widths in the typefaces that you use.