Concubinage
Concubinage is an interpersonal and sexual relationship between two people in which the couple does not want to, or cannot, enter into a full marriage. Concubinage and marriage are often regarded as similar, but mutually exclusive.

In China, until the 20th century, concubinage was a formal and institutionalized practice that upheld concubines' rights and obligations. A concubine could be freeborn or of slave origin, and her experience could vary tremendously according to her master's whim. During the Mongol conquests, both foreign royals and captured women were taken as concubines. Concubinage was also common in Meiji Japan as a status symbol.

Many Middle Eastern societies used concubinage for reproduction. The practice of a barren wife giving her husband a slave as a concubine is recorded in the Code of Hammurabi. The children of such relationships would be regarded as legitimate. Such concubinage was also widely practiced in the premodern Muslim world, and many of the rulers of the Abbasid Caliphate and the Ottoman Empire were born out of such relationships. Throughout Africa, from Egypt to South Africa, slave concubinage resulted in racially mixed populations. The practice declined as a result of the abolition of slavery.

In ancient Rome, the practice of concubinatus was a monogamous relationship that was an alternative to marriage, usually because of the woman's lesser social status. Widowed or divorced men often took a concubina, the Latin term from which the English "concubine" is derived, rather than remarrying, so as to avoid complications of inheritance. After the Christianization of the Roman Empire, Christian emperors improved the status of the concubine by granting concubines and their children the sorts of property and inheritance rights usually reserved for wives. In European colonies and American slave plantations, single and married men entered into long-term sexual relationships with local women. In the Dutch East Indies, concubinage created mixed-race Indian-European communities.

In the Judeo-Christian world, the term concubine has almost exclusively been applied to women, although a cohabiting male may also be called a concubine. In the 21st century, concubinage is used in some Western countries as a gender-neutral legal term to refer to cohabitation (including cohabitation between same-sex partners).
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