In Roman times, authors did not punctuate their texts.
The marking of pauses in a copy of a text was normally left to the initiative of
the individual reader, who would insert them or not according to the degree of
difficulty presented by the text, or the extent of his comprehension.
M.B. Parkes 1992
A short line used to connect the parts of compound words or the parts of a word divided for any purpose.
Hyphens are joiners. Use them to avoid ambiguity or to form a single idea from two or more words.
AVOID AMBIGUITY: Use a hyphen whenever ambiguity would result if it were omitted.
The president will speak to small-businessmen.
(Businessmen normally is one word, but without the hyphen we might infer that he was speaking to businessmen who are small.)
COMPOUND MODIFIERS: When a compound modifier two or more words that express a single concept precedes a noun, use hyphens to link all the words in the compound except the adverb very and all adverbs that end in ly.
A first-quarter touchdown.
A last-minute reprieve.
A bluish-green dress.
A full-time job.
A well-known man.
A better-qualified woman.
A know-it-all attitude.
A very good time.
An easily remembered rule.
Many combinations that are hyphenated before a noun are not hyphenated when they occur after a noun.
The team scored in the first quarter.
The dress, a bluish green, was attractive on her.
She works full time.
His attitude suggested that he knew it all.
When a modifier that would be hyphenated before a noun occurs instead after a form of the verb to be, the hyphen usually must be retained to avoid confusion.
The man is well-known
The woman is quick-witted.
The Associated Press Stylebook
For information about usage of the hyphen, click here
to consult one of the many style books listed on the Resources page