According to the groups in which the spouse is chosen from: Endogamy and exogamy

Endogamy is the practice of marrying only within a specific ethnic, social or religious group and rejecting people out of this group. The most common subcategory under endogamy is cousin marriages. A cousin marriage may be a parallel cousin or a cross cousin marriage. A parallel cousin is a cousin from the parent’s same sex sibling, like the child of the father’s brother or the child of the mother’s sister. A cross cousin is a cousin from the parent’s opposite sex sibling, like the child of the fathers’ sister or the child of the mother’s brother. While the rule of endogamy obliges people to marry within their group, the rule of exogamybans to marry from the same group. In exogamic societies, people should choose their spouse from outside their kin group.