**concubine**: A woman who is involved in a [monogamous] relationship with a man but is not legally married to him. An old term for a [kept woman] or girlfriend.
She is usually a willing participant in the relationship and may be of any [social status].
*Anne Boleyn was just a concubine in the eyes of her opponents and she was slandered as a homewrecker; [Katherine of Aragon] was [Henry VIII's] true queen in their eyes.
The harem of the palace did house the Sultan's wives and concubines, but it typically also housed all of the women of the palace, including his mother, sisters, aunts, and cousins.
Queen Catherine de' [Medici] resented her husband's dalliances with his much older concubine, Diane de Poitiers.
The senator's wife was indignant, barely containing her rage when she confronted her husband about the secret series of concubines that he had.*
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