Concubine

A concubine was a woman in a relationship with a man with no prospect of marriage.

At the beginning of the Klingon, a concubine named Karana was given the name and title of Shenara, daughter of Emperor of the Third Dynasty. 

In 2153, Zjod attempted to sell Jonathan Archer and Malcolm Reed a "quite skilled" Nuvian concubine. 

''In the mirror universe, the Denobulan $𝜇$ turned against $𝜇$ for the prospect of acquiring some concubines. $𝜇$ promised him he could choose as many as he wished.''