Direct dating affinity
Human kinship relations through marriage are commonly called "affinity" in contrast to the relationships that arise in one's group of origin, which may be called one's descent group.
In some cultures, kinship relationships may be considered to extend out to people an individual has economic or political relationships with, or other forms of social connections.
The major patterns of kinship systems that are known which Lewis Henry Morgan identified through kinship terminology in his 1871 work Systems of Consanguinity and Affinity of the Human Family are: The six types (Crow, Eskimo, Hawaiian, Iroquois, Omaha, Sudanese) that are not fully classificatory (Dravidian, Australian) are those identified by Murdock (1949) prior to Lounsbury's (1964) rediscovery of the linguistic principles of classificatory kin terms.
In many societies where kinship connections are important, there are rules, though they may be expressed or be taken for granted.
A descent group is a social group whose members talk about common ancestry.
A unilineal society is one in which the descent of an individual is reckoned either from the mother's or the father's line of descent.
In most societies it is the principal institution for the socialization of children.
It can be used in a more diffuse sense as in, for example, the news headline "Madonna feels kinship with vilified Wallis Simpson", to imply a felt similarity or empathy between two or more entities.
In biology, "kinship" typically refers to the degree of genetic relatedness or coefficient of relationship between individual members of a species (e.g. It may also be used in this specific sense when applied to human relationships, in which case its meaning is closer to consanguinity or genealogy.
There are four main headings that anthropologists use to categorize rules of descent.
They are bilateral, unilineal, ambilineal and double descent.
Kinship can also refer to a principle by which individuals or groups of individuals are organized into social groups, roles, categories and genealogy by means of kinship terminologies.