The concept of family systems has been used theoretically, metaphorically, and clinically in ways that have helped elucidate important aspects of family functioning and family life. With an emphasis on wholeness, interdependence, and patterned interactions, family systems have shaped how families are thought about, studied, and supported as they negotiate their interconnected lives across the life span. This entry describes theoretical perspectives of family systems, which include some of the central assumptions and constructs of family systems theory. This entry also discusses metaphorical perspectives, that is, some symbolic uses of the family as a system. Lastly, this entry notes some of the applications of family systems theory for intervention and therapy.