《礼记·曲礼下》
天子的配偶叫后，诸侯的配偶叫夫人，大夫的配偶叫孺人，士的配偶叫妇人，庶人的配偶叫妻。
天子之妃曰后，诸侯曰夫人，大夫曰孺人，士曰妇人，庶人曰妻。
The emperor's spouse was called 后, the feudal lord's spouse was called 夫人, the high-ranking official's spouse was called 孺人, the gentleman's spouse was called 妇人, and the commoner's spouse was called 妻.