This topic could also probably fit into the Academia Forum, but more likely, the folks here at the Wuxia Forum would be more knowledgeable in this area. Moreover, the topic *is* wuxia-related, albeit tangentially.
In Western royalty and nobility, the title of "princess" seems to be the catch all title for any woman belonging to the royal family or the upper echelons of the nobility who is not herself the monarch or the spouse of the monarch. A daughter of the reigning monarch is a princess, and so is her distant cousin. Obviously, they are not equals in rank, but their title is the same in English.
In the Chinese language, the distinction is much more precise. For example, Ah Chi in DGSD was referred to as a "gwun chu" of the Liao Empire after Siu Fung became a prince of the Liao Empire. Similarly, in HSDS, Chiu Mun, who was not a member of the royal family, but belonged to an important Yuan Dynasty noble family, also held the title of "gwun chu." In contrast, actual princesses that were descendants of monarchs, such as Princess Hua Jeng (daughter of Genghis Khan) in LOCH and Princess Fragrance from B&S: G&R, were "gung chu."
So is there an English equivalent for the term "gwun chu?"