However female Emperor means the Imperial members who succeed the Imperial blood line from these maternal relatives, and this does not concern whether the Emperor herself/himself is male or female, (Thus, there are both male and female emperors existing in the female lineage) so female Emperor and Emperor of the female lineage are basically two different words with different concepts.
しかしながら、女系天皇とはその天皇自身の性別に関わらず母方から皇室の血統を受け継ぐという血筋についての言葉である（したがって女系の男性天皇・女系の女性天皇の両方があり得る）ため、両者は本質的に異なる概念である。