The ranks of imperial consorts have varied over the course of Chinese history but remained important throughout owing to its importance in management of the inner court and in imperial succession, which ranked heirs according to the prominence of their mothers in addition to their strict birth order. Regardless of the age, however, it is common in English translation to simplify these hierarchy into the three ranks of Empress, consorts, and concubines. It is also common to use the term "harem", an Arabic loan word used in recent times to refer to imperial women's forbidden quarters in many countries. In later Chinese dynasties, these quarters were known as the back palace (後宮; hòugōng). In Chinese, the system is called The Rear Palace System (後宮制度; hòugōng zhìdù).