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one of the obligatory or preferable forms of marriage characteristic of clan and early class societies. There are two basic types of cousin marriage: cross-cousin, or marriage to the daughter of the mother's brother or of the father's sister; and ortho-cousin (parallel-cousin), or marriage to the daughter of the father's brother or of the mother's sister.
Cross-cousin marriage developed with dual organization and was the basic form of marriage in the clan society, since it assured the intermarriage of two exogamous families. With the decay of the clan, cross-cousin marriage was preserved only vestigially.
Ortho-cousin marriage developed at the same time and often became the preferred type, particularly the marriage to the daughter of the father's brother, which was common among the Arabs, Malagasy, part of the Bantu, and some of the peoples of Dagestan and Middle Asia. Marriage to the daughter of the mother's sister (as among the Tuareg) was less common. Because the ortho-cousin marriage allowed the retention of the property within the large family or other closely related group, it often became the preferable form of marriage.
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