What is the difference between a colon and a semi-colon?

I get this question a lot. People tend to confuse the two. First, a colon is this : while this ; is a semi-colon. If you think about the two as emoticons, the colon is straight forward looking at you, while the semi-colon is winking. Second, each has specific uses. Let's start with the colon. It is used after a complete sentence when what follows is either a list or a definition. For examples, see my post on the colon. The semi-colon is used most often between two complete sentences when the second sentence adds more information to the first. It has a poetic power when applied correctly, but it looks silly when misused. For examples, see my posts on semi-colons and on run-ons (under Option 2). Also semi-colons can be used to separate the items in a list -- instead of using commas -- if individual items in the list already contain commas. Otherwise, the overwhelming amount of commas would befuddle the meaning of the sentence.