A boundary line indicating the separation of land, territory, or area; a general term for borders, edges, or dividing lines on maps or properties.
隣地との境界線を確かめるために測量士が来た。
A surveyor came to check the boundary line with the neighboring land.
地図で二つの県の境界線が赤で示されている。
The boundary line between the two prefectures is shown in red on the map.
仕事と私生活の境界線を引くことは大切だ。
It's important to draw a boundary line between work and private life.