Practices controlling the relation of the sexes in the selection of marital partners.
Exogamous groups require their members to marry outside the group, sometimes even specifying the group into which members must marry. Such groups are usually defined in terms of kinship rather than politics or territory. Exogamy is usually characteristic of unilineal descent groups, in which descent is reckoned either patrilineally or matrilineally. In endogamous groups, marriage outside one's group may be forbidden, or there may merely be a tendency to marry within the group. Endogamy is characteristic of aristocracies and religious and ethnic minorities in industrialized societies but also of the caste system in India and of class-conscious nonliterate societies such as the Masai of East Africa.