(From L. familiam, immediate kinship; household and servants). Group of individuals who share some common domestic or nuclear condition. In botany and zoology the term f. designates a taxonomic group constituted by several natural genera that possess a large number of common characteristics. In mathematics f. refers to a set whose elements are grouped. For census purposes, the f. (household) is a complex unity of economic and social nature. In general, this designation refers to a group of persons who live together in the same residence and share meals. The single-person f. is constituted by a citizen who lives alone; the large f. consists of four or more children under 18 years of age or older disabled children unable to work. These categories vary according to the legislation of each country, depending on the degree of family protection and security provided and refers, among other cases, to single mothers with minor-age children. The f. plays a decisive role in the formation and socialization of the personality. It is a historical institution subject to change, and its specific characteristics vary from culture to culture. In recent years the f. has undergone vertiginous changes due, in large part, to urban overcrowding. Large families have had to reduce their size due to the spatial limitations of land for residential housing. The growing incorporation of women into the working world outside the home has also had an effect. In general, as the standard of living of populations rises, f. size tends to shrink and, inversely, in poor countries explosive growth in family size can be observed. Currently, new structures are emerging that replace parts of the traditional f., for example, in the care and supervision of children in day-care centers. Adoption as well as advances in artificial insemination introduce variants in the concept of the traditional f., bonded by consanguinity. Another case is that of families formed by homosexual parents and adopted children. N.H. warns of the urgent need to lower the birthrate, improving the standard of living of families in poor countries; it supports legislative initiatives to protect the rights of mothers and children and encourages the creation of inter-family associations capable of providing a complete preschool education.