1A boundary or dividing line that separates two things, places, or concepts — used for both concrete borders (like land boundaries) and abstract limits.
二つの県の境界はこの川に沿っている。
The boundary between the two prefectures runs along this river.
仕事と私生活の境界があいまいになっている。
The boundary between work and private life has become blurred.
隣の家との境界にフェンスを立てた。
We put up a fence at the boundary with the neighboring house.
その病気の症状と正常の境界を見極めるのは難しい。
It's difficult to determine the boundary between the symptoms of that illness and a normal condition.