What's up with Em 'n' En?

Hyphens, em dashes, en dashes—who ever knew there were so
many to choose from. Here’s how to make the right choice.

Hyphens are the smallest member of the dash family.
They’re strictly for hyphenating words or numbers, and
you’ll find them in phone numbers or in adjectives
(such as “red-hot” or “tailor-made”) as well as
compounds starting with “long” (e.g., “long-winded”)
or “self” (e.g., “self-conscious”).

An en dash is approximately the width of an
uppercase N in that particular font. Use it
between words to indicate duration, a range,
or where you might otherwise use “to”. You
can leave a little space on either side of an en
dash, but not a full character space. In many
publications, it has replaced the em dash.

An em dash is approximately the width of an
uppercase M. The em dash is often used where a
period is too strong and a comma is too weak.
Used in a similar manner as a colon or
parenthesis, it can indicate an aside or abrupt
change in thought. The em dash should be used
without any spaces on either side.