Concubine – A secondary wife of inferior social and legal status.
God used this word 39 times in Scripture, all of which are in Israel’s Masoretic Text Old Testament.
In Scripture, having more than one wife is not forbidden or even derogatory.
A concubine is simply a wife that does not have any legal authority to encumber the household or dire. She is a subordinate wife, having no authority to modify or guide the house. Her status is above a servant, but less than a titled wife.
In Scripture, multiple wives were common. But Christianity, being contrary to Scripture, has made having multiple wives and concubines illegal in most of the Western-World, and Presumed Public Knowledge has attached a very negative connotation to the practice.
Today, concubines still exist, but in ignorance, people call them mistresses.
See also Christian, Harlot, Married, Mistress, Prostitute, Whore, Wife