A mistress is a man’s long term female sexual partner and companion who is not married to him, especially used when the man is married to another woman. The relationship is generally stable and at least semi-permanent; however, the couple do not live together openly. Also, the relationship is usually but not always secret, and there is the implication that a mistress may be “kept”, i.e. that the man is paying for some of the woman’s living expenses, or provides her with an allowance.
The term can also be used to describe the “other” companion in a female same-sex marriage. Likewise, a woman may be married to a man and have a mistress of her own.
Unlike a concubine, a mistress has no legal relationship to the man.
There is no specific word in English for a “male mistress”, a man in the same relationship to a woman as a mistress is to a man, except for the more general term “lover”, which does not carry the same implications. In 18th- and 19th-century Venice the terms “cicisbeo” and “cavalier servente” were used to describe a man who was the professed gallant and lover of a married woman.
Historically, the term has denoted a kept woman, who was maintained in a comfortable (or even lavish) lifestyle by a wealthy man so that she will be available for his sexual pleasure. Such a woman could move between the roles of a mistress and a courtesan depending on her situation and environment. Today however, the word mistress is used primarily to refer to the female companion of a man who is married to another woman; in the case of an unmarried man it is usual to speak of a “girlfriend” or “partner.”
Historically a man “kept” a mistress. As the term implies, he was responsible for her debts and provided for her in much the same way as he did his wife, although not legally bound to do so. In more recent and emancipated times, it is more likely that the mistress has a job of her own, and is less, if at all, financially dependent on the man.
A mistress is not a prostitute. While a mistress, if “kept”, may essentially be exchanging sex for money, the principal difference is that a mistress keeps herself exclusively reserved for one man, in much the same way as a wife, and there is not so much of a direct quid pro quo between the money and the sex act. There is also usually an emotional and possibly social relationship between a man and his mistress, whereas the relationship to a prostitute is predominantly sexual.
