Other forms: concubines
Throughout history, there have been instances when it was considered acceptable for an important man to keep a woman, not his wife, as a mistress. These women were called concubines, and they often were treated better than the man’s wife.
The word concubine comes from the Latin verb, cubare, which means "to lie down." The word developed in Middle English in the 13th Century, and is another name for a woman taken as a mistress. The practice was common throughout history: the Bible includes many references to concubines, and in ancient China, a ruler might have had thousands of concubines, some treated well, some like prostitutes. Sad to say, the practice is still going on, acceptable in some countries today.