A dash ( -- ) can act as a colon or a semicolon; paired dashes may
act
as parentheses. Information connected to a dash or dashes is
emphasized.
Using Dashes Properly
1) Use a dash to indicate a sudden break in thought or a shift in tone.
Betty does not care which boy she dates—she likes them both.
2) Use a dash to introduce an explanation, an illustration, or a series.
He limited his choices to two colors—red and green.
3) Use a dash or dashes to set off asides.
That test—and one should use that word loosely—was too simple.