In human context, a family (from Latin: familiare) is a group of people affiliated by consanguinity, affinity, or co-residence. In most societies it is the principal institution for the socialization of children. Extended from the human "family unit" by biological-cultural affinity, marriage, economy, culture, tradition, honour, and friendship are concepts of family that are physical and metaphorical, or that grow increasingly inclusive extending to community, village, city, region, nationhood, global village and humanism. A family group consisting of a father, mother and their children is called a nuclear family. This term can be contrasted with an extended family.
There are also concepts of family that break with tradition within particular societies, or those that are transplanted via migration to flourish or else cease within their new societies. As a unit of socialization and a basic institution key to the structure of society, the family is the object of analysis for sociologists of the family. Genealogy is a field which aims to trace family lineages through history. In science, the term "family" has come to be used as a means to classify groups of objects as being closely and exclusively related. In the study of animals it has been found that many species form groups that have similarities to human "family"—often called "packs."