1. the processes, operations, and changes that occur within social groups, which affect patterns of affiliation, communication, conflict, conformity, decision making, influence, leadership, norm formation, and power. The term, as used by Kurt Lewin, emphasizes the power of the fluid, ever-changing forces that characterize interpersonal groups. See also intergroup dynamics.

2. the field of psychology devoted to the study of groups and group processes.

3. a conceptual and clinical orientation in group psychotherapy that explicitly recognizes and explores group-level processes in the treatment group.