A queen (of imperial family) is a female who is in the direct line and in the third or more degree of kinship from the emperor (not in a collateral line, and counted from the emperor who was a direct ancestor) according to the Imperial House Law.
皇族における女王（じょおう/にょおう）とは、皇室典範では天皇からみて直系で三親等以遠の女子を指す（傍系でなく直系尊属の天皇から数える）。