Kinship is both a social web and an anthropological subject
In anthropology, kinship names the relationships that structure human lives in every society, even when local maps differ sharply. The word covers lived patterns of relatedness and the scholarly study of those patterns, including ties by descent and by marriage.
Kinship organizes people into groups, roles, categories, and genealogies that allocate rights and duties. Descent ties and marriage alliances intertwine so that in-laws and blood kin share overlapping obligations. In a looser sense, kinship can mean affinity based on shared traits among any entities being compared.
Anthropologist Robin Fox framed the subject as what people do with basic facts of life such as mating, gestation, parenthood and socialization. Biologists use the word more narrowly for degrees of genetic relatedness, as in kin selection theory. Family itself may rest on recognized birth, on marriage, or on living and eating together, and in most societies it is the main setting where children are socialized; where labour is split by sex, marriage is also needed to form an economically productive household.
Societies label relatives differently. Some languages separate uncles by blood from uncles by marriage, while others use one word for a father and his brothers. A descriptive terminology gives each relationship its own term, whereas a classificatory one bundles several under a single word. In his 1871 Systems of Consanguinity and Affinity of the Human Family, Lewis Henry Morgan identified the Iroquois, Crow, Omaha, Inuit, Hawaiian and Sudanese patterns. Murdock described those six in 1949, before Lounsbury's 1964 rediscovery of the linguistic logic behind classificatory terms; a seventh, Dravidian, was recognized as distinct later, and most Australian Aboriginal systems are classificatory too. Some languages even have trirelational kin terms that express a link among three people at once.
Source: Kinship
