11.1. Punctuation http://www.ck12.org
In this case, the phrase that comes after the dash is more important than the independent clause that comes before.
Example 2- To some of you, my proposals may seem radical—even revolutionary. Here the dash works in
conjunction with “even” to emphasize the adjective “revolutionary.”
Example 3- The cousins—Tina, Todd, and Sam—arrived at the party together. Here the dash is not being used for
emphasis, but to stand in the place of additional commas that might confuse the reader.
Whereas dashes are used to emphasize content, parentheses are used to downplay content. They place less emphasis
on the enclosed content than commas. Use parentheses to set off nonessential material—such as dates, clarifying
information, clarifying information, or sources—from a sentence
Example 1- Muhammad Ali(1942-present), arguably the greatest boxer of all time, claimed he would “float like a
butterfly, sting like a bee.”
Example 2- Denis Johnson’s new novel(whichisboundinaluminousredhardbackcover) is a worthy addition to
the crime fiction genre.
Notice that information enclosed in parentheses has little relevance to the primary idea or meaning of the sentence.