Writers often use the hyphen to form compound terms, but the character is also used for dividing words, especially in professionally printed material. Look for specific compound terms, nouns and verbs in a dictionary to determine whether they need to be written with a hyphen. Compound adjectives follow different rules and are generally not found in dictionaries.
While there are no set rules for the use of hyphens in compound terms, writers must memorize the difference open compound terms such as "car wash" and hyphenated ones such as "check-in." Compound adjectives need to be hyphenated when two or more words collectively act as an adjective and appear directly before the noun being modified. Examples include "know-nothing voters," "26-year-old man" or "cash-back guarantee."
The main exception to this rule is when the compound adjective's first word is an adverb that ends in "-ly". As an example, there is no hyphen in the phrase "That is a magnificently made work of art". However, if that adverb is not the first term within a larger compound adjective, it should be hyphenated. An example of a hyphenated compound adjective with an adverb of this type in it would be "This not-so-magnificently-made work of art will never sell."
Word processors and typesetters generally use hyphens to divide words in printed material when a single word needs to take up space at the end of a line while continuing at the beginning of the next line. Readers can see this particular hyphen use in magazines, books and newspapers.