Berdel
Berdel marriage or sibling swapping, is a type of marriage wherein a bride or bridegroom is exchanged with a bride or bridegroom of another family. It is common in a few Kurdish communities as well as some Sub-Saharan African cultures. The relatives giving their bridegroom or bride away are typically well-acquainted or friends with the other family. The popularity of berdel marriage is sometimes attributed to the fact that it costs less as there is no dowry, bridewealth or similar exchange of monetary transaction. Another cause for its popularity is that it cements the friendship that already  existed between the exchanging families. Since there are four people getting married, such a marriage is often referred to as a "parallel marriage" or "four-way marriage". In the event where a family officiant offers a woman to the other family, it is sometimes referred to as "sister swapping", "daughter swapping" or "niece swapping". The male counterpart to the same situation is referred to as "brother swapping", "son swapping", or "nephew swapping" respectively. In Turkey, 5% of marriage are berdel marriages, and are called "degis tokus", while in Arab countries such marriages are called "sigar".