Federal Rule of Civil Procedure 23(a)
Definition
A rule establishing the prerequisites for certifying a class. The class may be certified if the following requirements are met: (1) the class members are too numerous to make joinder practicable, (2) class members’ claims contain common questions of law or fact, (3) the named representative's claims or defenses are typical of the class members’ claims or defenses, and (4) the representative party will fairly and adequately protect the class members’ interests.