Proper parties are ones whose interest may be affected by a judgment, but whose presence is not essential in order for the court to adjudicate the rights of others. Proper parties may be added to a lawsuit through a permissive joinder.
Example: In an action for negligence where two defendants are jointly and severally liable, each defendant is a proper party. The plaintiff has a right to sue either of the defendants, but only one of the defendants is required.
[Last updated in July of 2020 by the Wex Definitions Team]