Res judicata or res iudicata (RJ), also known as claim preclusion, is the Latin term for "a matter [already] judged", and may refer to two concepts: in both civil law and common law legal systems, a case in which there has been a final judgment and is no longer subject to appeal; and the legal doctrine meant to bar (or preclude) continued litigation of such cases between the same parties, which is different between the two legal systems. In this latter usage, the term is synonymous with "preclusion".