A hyphen ( - ) is used to link parts of a compound word. This includes most dual heritages (Mexican-American), and all words in a compound modifier except "very" and adverbs that end in "ly." (The Broncos scored a first-quarter touchdown.)
Use a hyphen to form a single idea from two or more words (socio-economic), and whenever its omission would change the meaning of a phrase. (President Dunn will speak to small-businessmen.)
A hyphen can also be used to avoid duplicated vowels and tripled consonants (anti-oppression, pre-empt, hill-like).
A dash is expressed as an "em dash" ( — ) in printing, is expressed in plain text as two hyphens ( -- ) and is used in place of a comma, colon or semicolon for greater emphasis. It denotes a major break or pause and should not be overused.
President Dunn introduced the plan—the first of its kind—at a public forum.
He defined core values—inclusiveness, sustainability, responsibility and respect.
Traditionally, a dash is preceded and followed by a space, but more recently, spaces have been omitted. For consistency in University writing do not include spaces.
Em dash and en dash
An em dash is the width of the letter "m" in the font and type size being used, and should never be used in place of an en dash or hyphen.
An en dash is the width of the letter "n" and is expressed in plain text as a hyphen ( - ). A traditional use of the en dash is in dates (2012-13), but since it is largely indistinguishable from a hyphen, the en dash is no longer in common use. Use a hyphen.