In the Chinese imperial system, 妃 was a rank below 皇后 (huánghòu, empress). The emperor could have multiple 妃, organized into a strict hierarchy: 贵妃 (noble consort), 淑妃 (virtuous consort), 德妃 (consort of virtue), 贤妃 (worthy consort).
usage
Modern usage: 王妃 (wángfēi) means princess consort (wife of a prince), used for foreign royals like 戴安娜王妃 (Princess Diana). 妃子 (fēizi) specifically means imperial concubine.
