a border or a rule that shows the limits of something or how things are divided

The river serves as the line of demarcation (= the line showing the separation) between the two counties. 那条河是两国的分界线。

In some schools there is little demarcation between subjects (= subjects are not taught separately). 在某些学校里，各学科之间几乎没有明确的界限。

On this map, demarcations between regions are shown with dotted lines. 这张地图用虚线标出了地区分界线。