Defamation is a false statement of fact that (1) is published; (2) damages or injures the reputation of another party; and (3) is made without legal excuse (defense or privilege). Defamation may be in the form of a written statement (libel) or a spoken statement (slander) and is a tort or legal wrong that may create civil liability (for money damages) for a person who makes a defamatory statement that is not privileged (e.g., made during a judicial proceeding) and for which there is no defense (such as truth or retraction).

To be actionable and subject the person making the statement to liability the statement must be published to a third party. In other words, a written or spoken statement made from one person to another that is not read or heard by a third person (or could not have been reasonably expected by the person making the statement to be read or heard by a third person) is not published and is not defamation.

In California, defamation is recognized as a false statement of fact that is published, injures someone's reputation, and is made without a legal excuse. Defamation can be categorized as either libel, if it is written, or slander, if it is spoken. For a defamation claim to be actionable in California, the statement must be communicated to a third party; a private statement between two people that is not overheard or seen by others does not constitute publication and therefore is not considered defamation. The plaintiff must prove that the statement caused damage to their reputation. Defenses against defamation include truth, which is an absolute defense, and retraction, which can mitigate damages. California law also recognizes certain privileged communications, such as those made during judicial proceedings, which are immune from defamation claims. It is important for individuals to consult with an attorney to understand the nuances of defamation law in California, including the specific requirements for proving a claim and the available defenses.