This work discusses marriage as a social institution, in the strict sense of the term. Contents: origin of marriage; frequency of marriage and the marriage age; endogamy; exogamy; marriage by capture; consent as a condition of marriage; marriage by consideration and by the exchange of presents, gifts to the bride and to the bridegroom; marriage rites; monogamy and polygamy; polyandry and group marriage; and duration of marriage and the right to dissolve it.