Grammar Smart 3rd Edition - Princeton Review 2014

H. The Dash
PART 4. Punctuation

Dashes can be used in place of a colon or parentheses. Some people feel that dashes signify greater emphasis. Whether you use dashes is your choice—they are optional.

Rules For Dashes

1. Use one dash in place of a colon, following the rules for colons.

We finished our tasks in record time—one hour!

Or: We finished our tasks in record time: one hour!

2. You can use dashes instead of parentheses.

If you come to my house—take a left after crossing the bridge—please bring some turnips and an oboe.

Or: If you come to my house (take a left after crossing the bridge) please bring some turnips and an oboe.