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 Illinois, defamation is recognized as a false statement of fact that is published, injures another party'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 Illinois, the statement must be communicated to a third party; a private exchange between two people that is not exposed to others does not constitute publication. The injured party must prove that the statement caused damage to their reputation. Defamation is a civil wrong, and the person who made the defamatory statement can be held liable for monetary damages. Defenses against defamation claims include truth, privilege (such as statements made during judicial proceedings), and, in some cases, retraction. Illinois law requires a plaintiff to prove actual malice to prevail in a defamation claim against public officials or public figures, which means showing that the statement was made with knowledge of its falsity or with reckless disregard for the truth.