What is Endogamy?

What is Endogamy?:
Endogamy is the practice of tribal groups limiting marriage to members of the group and prohibiting marriage outside the group (exogamy). Endogamy is more common in socially stratified societies, and is most common among aristocratic and ruling classes. European royalty traditionally limited marriage to other members of royalty and denigrated marriage to “commoners,” even if of the same nationality. The purpose of endogamy is to preserve the “purity” of bloodlines which might become “polluted.”