This institution has been with mankind since before recorded history and has appeared under a variety of forms throughout history. It transcends cultures and religions. The Catholic Church recognizes a spiritual element in the matrimonial bond beyond the simple fact of biological union, and therefore recognizes it as a great work of God’s grace.  Canon Law gives the following definition of matrimony:

The matrimonial covenant, by which a man and a woman establish between themselves a partnership of the whole of life, is by its nature ordered toward the good of the spouses and the procreation and education of offspring; this covenant between baptized persons has been raised by Christ the Lord to the dignity of a sacrament (CIC, 1055 § 1)

For Further Discussion: Marriage in God's Plan; The Ends of Marriage; The Sacrament of Matrimony; Separation; Civil Marriages; Virginity for the "Sake of the Kiongdom of Heaven."