Many thanks for posting anything on hyphen usage!!!
In print a hyphen (-) is half the length of a dash (–),
but in writing there is often little noticeable difference.
While the dash has the purpose of separating
words and groups of words, the hyphen is
meant to link words and parts of words. The use of
hyphens is very variable in English, but the following
guidelines reflect generally agreed principles.
The hyphen is used to join two or more words so
as to form a single word (often called a compound
word), e.g. free-for-all, multi-ethnic, right-handed,
and punch-drunk. Straightforward noun compounds
are now much more often spelled either as
two words (boiling point, credit card, focus group)
or as one, even when this involves a collision of
consonants, which used to be a reason for putting
in the hyphen (database, earring, breaststroke). In
American English compound nouns generally
written as two words in British English are often
written as one word.
There are two cases in which a compound
spelled as two words is made into a hyphened
form or a one-word form:
1. when a verb phrase such as hold up or back up is
made into a noun (hold-up, backup);
2. when a noun compound is made into a verb
(e.g. a date stamp but to date-stamp). Note that
a normal phrasal verb should not be hyphenated:
write continue to build up your pension not
continue to build-up your pension.
A hyphen is often used:
1. to join a prefix ending in a vowel (such as co- and
neo-) to another word (e.g. co-opt, neo-
Impressionism), although one-word forms are
becoming more usual (cooperate, neoclassical).
2. to avoid ambiguity by separating a prefix from
the main word, e.g. to distinguish re-cover (=
provide with a new cover) from recover and re-sign
(= sign again) from resign.
3. to join a prefix to a name or designation, e.g.
4. to stand for a common second element in all but
the last word of a list, e.g. two-, three-, or four-fold.
5. to clarify meanings in groups of words which
might otherwise be unclear or ambiguous (e.g.
twenty-odd people came to the meeting).
You should also use a hyphen to clarify the meaning
of a compound that is normally spelled as separate
words, when it is used before a noun: an up-to-
date record but the record is up to date.
There is no need to insert a hyphen between an
adverb ending in -ly and an adjective qualified by
it, even when they come before the noun: a highly
competitive market, recently published material.
When the adverb does not end in -ly, however, a
hyphen is normally required to make the meaning
clear when the adverb precedes the noun: a well-known
woman (but the woman is well known).
taken from Oxford's Guide to Good English