(Quoted from Wikipedia)
Although laws vary by state, in the United States a defamation action typically requires that a plaintiff claiming defamation prove that the defendant:
1.made a false and defamatory statement concerning the plaintiff;
2.shared the statement with a third party (that is, somebody other than the person defamed by the statement);
3.if the defamatory matter is of public concern, acted in a manner which amounted at least to negligence on the part of the defendant; and
4.caused damages to the plaintiff.
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