The difference between libel and slander

Question

I've heard people use the terms libel and slander interchangeably, but I know that they are different in the eyes of the law. What are the defining characteristics of each?

Answer 1

From http://grammarist.com/usage/libel-slander/:

(emphasis mine)

Libel is the use of false, defamatory claims about someone in written or printed form. Slander likewise denotes false statements that damage a person’s reputation, but it is committed orally or in any other transient form

So a false claim satisfying the definition of defamation would be libel if written (including on the Internet, per Varian Medical Systems, Inc. v. Delfino), and slander if made in a transient form.