Hyphens and Dashes
Though they may have been identical in the day of the typewriter, dashes and hyphens are not the same thing in typography. Visually, a hyphen is a very short line, whereas an en dash is wider, and an em dash wider still: historically, the width of a lower case* n and m respectively in the days of metal type.
* Also from the days of metal type, lower case letters were stored in the physical lower case, with upper case (capitals) in the upper case.
A hyphen is used to join the two (or more) parts of a compound word to show that they function as a single unit:
[See also Hyphenated compound words below.]
An en dash is used to separate a range of numbers, directions or scores (used in place of ‘to’):
See pages 12–24
Liverpool beat Spurs by 2–0
… or to show a change in the writer’s thought resulting in a change in sentence structure:
William Blake – English poet, painter and printmaker – was largely unrecognised in his lifetime.
The em dash is a little-used – some might say old-fashioned – alternative for the latter use, usually employed without a space on either side:
William Blake—English poet, painter and printmaker—was largely unrecognised in his lifetime.
Really, though, in the question of en or em dash it’s really a matter of subjective, aesthetic opinion – which may be affected by the actual widths of em or en dashes in the typeface being used – and, of course, consistency.
Hyphenated compound words
There are many rules in grammar relating to the use of the hyphen in compound words. In most cases a compound adjective is hyphenated if placed before the noun it modifies, but not if placed after the noun:
a long-term solution
a solution for the long term
If in doubt, consult your dictionary!
Using an en dash with complex compound adjectives
An En Dash can also be used for clarity, as well as a more pleasing appearance, when one of the elements in a compound adjective is an open compound (two words with a space between):
My great-grandfather flew World War II–era spitfires
My great-grandfather flew World War II-era spitfires
How do I type an en dash?
You may find that up-to-date versions of MS Word will do this for you. On a Mac you would type
option + minus for an en dash, or
option + shift + minus for an em dash.
You may find that your organisation has a writing style guide covering the use of punctuation and other special characters. To ensure consistency across all corporate communications, internal and external, you should follow these if they exist.