A compound adjective is a modifier made up of two or more words. The general practice in writing is to use a hyphen if the compound adjective can be misread. There are several exceptions to this rule. The best reference for confirming whether to hyphenate or not hyphenate a word is Webster’s dictionary (11th edition). Here are five rules for using the hyphen.
Use a hyphen with comparative and compound adjectives (words ending in er and est).
Examples: longer-term study, best-qualified candidate, highest-rated schools.
Use a hyphen in a temporary compound adjective (one that is made up of specially chosen words to best describe something). The hyphen is a crucial tool to give clarity and help readers understand your message. Use it if the word can be misread to change the meaning of your sentence.
Example: The students resided in two parent homes. (This implies two separate residences.)
The students resided in two-parent homes. (This implies that they lived in a home with both of their parents.)
Example: The used-furniture store is popular with students. The hyphen in this case shows that the store sells used furniture.
Whereas “The used furniture store ” implies that the furniture store is used by students.
Use hyphens for compound words in which the second word is capitalized.
Example: The program will operate from mid-June to the end of August.
When there is a prefix before a date.
Example: The pre-1945 movie was not included in the curriculum.
Example: The pro-MADD parents sponsored after-prom activities for the seniors.
Several related words.
Example: The non-school-based employees work for 12 months of the year.
Words that could easily be misunderstood.
Example: re-form (to form again)
Most words formed with a prefix or suffix are written as one word.
Examples: Prefix: extracurricular, socioeconomic, prekindergarten (BUT pre-K), counterclockwise
Suffix: ladylike; courthouse
If a compound adjective is placed after the term it describes, do not use a hyphen, since the combination is clear enough for readers to understand.
Examples: the student-centered activities are new this year, BUT this year, the new activities are student centered.
The program was designed for same-sex children. BUT The program was designed for children of the same sex.
When two or more compound adjectives have a common base, the base is often omitted in all but the last adjective, but the hyphens are retained, followed by a space.
Examples: Long- and short-term measures, over- and underfed hamsters, 15- and 30-year mortgages.
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