Res judicata (RJ) or res iudicata, well known as claim preclusion, if we look in the Latin term for matter decided and refers to either of two concepts in both civil law and common law legal systems: a case in which there has been a final judgment and that is no longer subject to appeal; and the legal doctrine meant to bar.

On the opposite side of res judicata, the word Res judicata bars the parties from filing the suit, whereas sub judice bars the trial between the parties. In res judicata, the suit must be decided in the competent court, but in res sub, the suit must be pending before the competent court.