Guniang

Guniang means a young, unmarried woman. Strangers use it the way English speakers might say "young lady" or "miss": a shopkeeper greeting a customer, a hero asking a woman he has just met for her name. It's polite without being formal.

In historical dramas, it also works as a household title. Servants in a well-off family call the daughters guniang, often with a number for birth order, so you'll hear "Sixth guniang" where subtitles say "Sixth Miss." In that sense it overlaps with xiaojie, and which word a drama uses depends partly on the period it's set in.

The Story of Ming Lan, set in the Song dynasty, uses guniang for the daughters of the Sheng family, and the numbering matters: birth order, and whether a daughter's mother is the main wife or a concubine, shape how each girl is treated.

As a description rather than a form of address, guniang simply means a girl or young woman. "A good guniang" is high praise from an older relative.

Note that gu on its own is part of other family terms, such as gugu, a father's sister. And in palace dramas, senior palace maids are addressed as gugu, a different role entirely.

The male counterpart in older usage is gongzi, young master, which you'll hear for the sons of good families. Brothers and close older friends are gege.