Domain
Territory, Realm
noun, の adjective
This is my territory. This is my region. This is my domain!
This is a jukugo word, which usually means on'yomi readings from the kanji. If you know the readings of your kanji you'll know how to read this as well.
各領域のボーダーを明確にしたほうがいい。
It is better to clarify the boundaries of each area.
これはもう、科学の領域ではないんです。
This is no longer within the realm of science.
誰でも、前進するためには未知の領域に足を踏み入れなくてはいけない。
Everyone has to take a step into unknown territory to progress.