you have ever looked closely at one of the P22 key charts you will
notice several dashes, well, six to be exact. These dashes are the
hyphen, minus sign, en dash, em dash, macron and underscore. Don't
stop reading! These dashes are found in every font because each has
a specific typographic and grammatical use, but you'll probably need
to use only three of them.
The Hyphen -
The hyphen is the shortest dash visually. It is the most widely misused
dash because people employ it for all sorts of purposes, although
it is meant only for hyphenating words or creating line breaks.
The minus sign is slightly longer than the hyphen, usually the same
length as the en dash. Obviously one uses the hyphen in mathematical
formulas and equations. The minus sign is usually designed to be
the same length as the plus and equals signs. In most fonts these
are usually monospaced along with the numbers for ease when being
used in tabular formats.
The en dash gets its name because it is approximately the width of
the capital N in any particular font. Use the en dash when indicating
duration, such as when you could substitute the word "to." You
can set the en dash with a little space on either side if you wish,
but do not use a full space:
For ages 3–5
You would also use an en dash when you have a compound adjective,
one part of which consists of two words or a hyphenated word:
New York–London flight
pre–World War II period
As a rule, the em dash is twice as long as the en dash. This dash
is the length if the capital M in any particular font. The em dash
is used in much the way a colon or set of parentheses is used: it
can show an abrupt change in thought or be used where a period is
too strong and a comma too weak. An em dash should never be used
with spaces on either side although, clearly, many people are unaware
of this rule.
The Macron ¯
The Macron is a diacritic used to mark long vowels in many languages
such as Latvian, Lithuanian, Hausa and Fijian, among others. The
macron is also necessary for romanized Arabic, Greek, Hebrew, Japanese
and Sanskrit. This dash, if you can call it a dash, is usually placed
in the font to hang above a lower case letter. If you ever need to
use a macron, you may need to do some special kerning and baseline
shifting to position it correctly.
The Underscore (or Lowline) _
The underscore is another diacritic required for many African and
Native American languages. It is also useful for some purposes in
English and is becoming fairly common in e-mail addresses. The underscore
is sometimes used as an underdot in romanized Arabic and Hebrew.
You may never have a need to use this dash for underlining because
most text applications have a built-in underscore feature.