CONCUBINAGE sometimes expresses a criminal or prohibited commerce between the two sexes; in which sense it comprehends adultery, incest, and simple fornication.
In its more restrained sense, concubinage is used for a man's and a woman's cohabiting together in the way of marriage, without having passed the ceremony thereof.
Concubinage was anciently tolerated: the Roman law calls it an allowed custom, licita consuetudo. When this expression occurs in the constitutions of the Christian emperors, it signifies what we now call a marriage in conscience.
The concubinage tolerated among the Romans in the time of the republic, and of the heathen emperors, was that between persons not capable of contracting marriage together; nor did they even refuse to let inheritances descend to children which sprung from such a tolerated cohabitation. Concubinage between such persons they looked on as a kind of marriage, and even allowed it several privileges; but then this concubinage was confined to a single person, and was of perpetual obligation as much as marriage itself. Hottoman observes, that the Roman laws had allowed of concubinage long before Julius Cæsar made that law whereby every one was allowed to marry as many wives as he pleased. The emperor Valentinian, Socrates tell us, allowed every man two.