What's the difference between defamation and slander?

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  It appears that slander has more to do with oral communication whereas defamation includes written communication:

  slan·der (slan’d?r) n.

Law. Oral communication of false statements injurious to a person’s reputation. A false and malicious statement or report about someone.

  def·a·ma·tion (def’?-ma’sh?n) n.

The act of defaming; calumny.

  de·fame (di-fam’) tr.v., -famed, -fam·ing, -fames.

To damage the reputation, character, or good name of by slander or libel. See synonyms at malign. Archaic. To disgrace.

  li·bel (li’b?l) n.

A false publication, as in writing, print, signs, or pictures, that damages a person’s reputation. The act of presenting such material to the public.