The concept of the nuclear family is used to designate a socially meaningful unit of family members. In this entry, the use of the concept of the nuclear family is positioned in two perspectives. First, when defined by demographic criteria, the nuclear family refers to a residential unit. Second, when adopting a structural functionalist perspective, the nuclear family refers to a functional unit featuring specific interactions between genders and generations. Criticism of the concept of the nuclear family as well as conceptual changes and further developments are discussed.