The definition of marriage has changed considerably over time. In ancient times marriage was a covenant based relationship; laws governed the choice of partners in Hebrew culture whereas in Greek and Northern Europe a bride was either purchased or captured. In the 15th and 16th century, Church and other religious authorities were heads of the institute of marriage. Today marriage is the product of centuries of change in custom and law. The concept of marriage varies with culture, however, government and religious laws dictate it. (How the definition of marriage has changed over time)
Marriage, as agreed by everyone, is a fundamental social institution. A social institution is the “network of shared meanings, norms, definitions, expectations and understandings held by the members of a society” (Traditional Marriage is Essential for a Healthy Society). This institution is universal, existing in all cultures since pre history. Though the dynamics of marriage have changed over the centuries, the concept of the institution is still to encourage procreation, ensuring a stable family structure in which children will be