Res judicata prevents relitigation of finally adjudicated matters but allows flexibility where overriding public interest arises. The doctrine of res judicata bars parties from relitigating matters finally adjudicated by a competent court, applying to the matter in issue-the right claimed and the facts and law adjudicated as the foundation of that right-rather than to the reasons for judgment. It conclusively binds issues of fact or mixed law and fact between the same parties, but does not ordinarily extend to pure questions of law unrelated to operative facts. Res judicata is limited where the cause of action differs, the law has changed, jurisdiction was in issue, or public interest considerations warrant a flexible approach.