Use a hyphen to link words such as compound words and adjectives. Basically, if the words don’t make sense on their own, use a hyphen.  For example: full-time faculty.  Do “full faculty” and “time faculty” make sense?  They don’t, so use a hyphen.

a nine-year-old girl

full-time faculty

Omit the hyphen if the compound adjective follows the noun.

She is nine years old.

They work full time.

 

Some words are always hyphenated, like e-mail. However, some words are only hyphenated when they precede a noun and are used as an adjective.

Joe Davis lives on campus.

Joe Davis is looking for on-campus housing.

Susan Smith takes classes full time.

Susan Smith is a full-time student.

Adjunct faculty teach part time.

Some faculty members teach on a part-time basis.

 

There is no need for a hyphen after a word that ends in “ly.”

The college is a highly respected college.