事故发生的具体位置已被警方标记出来。

The exact ___locus of the accident has been marked by the police.

这个广场是城市社交活动的中心。

The square serves as the ___locus for the city's social activities.

在几何学中，圆的轨迹是与固定点等距的所有点的集合。

In geometry, the ___locus of a circle is the set of all points equidistant from a fixed point.