Writing Tip: The Colon and the Dash

What's the difference between the colon ( : ) and the dash ( -- )?

1. Colons are used after independent clauses to introduce lists, appositives, or illustrations. They should not separate verbs from their complements or prepositions from their objects.

Correct
A perfect sandwich requires three ingredients: bread, peanut butter, and jelly.

Incorrect
A perfect sandwich requires: bread, peanut butter, and jelly.

2. Dashes are used for abrupt interruptions or to announce a long summary or appositive. The dash is less formal than a colon or parentheses.

Then they saw a horrifying sight--a huge, hissing, angry rattlesnake.

His only excuse for his behavior--if there even is one--was that he had been drinking.