• noun:   (law) a proceeding that permits a person to enter into a lawsuit already in progress; admission of person not an original party to the suit so that person can protect some right or interest that is allegedly affected by the proceedings

  Example: "The purpose of intervention is to prevent unnecessary duplication of lawsuits"

• noun:   the act of intervening (as to mediate a dispute)
• noun:   a policy of intervening in the affairs of other countries

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