The perpendicular distance from the base of a geometric figure to the opposite vertex, parallel side, or parallel surface. 顶垂线，高线从一个几何形体的底边到相对的顶点、平行边或平行面的垂直距离
A family of geometric objects, such as lines, that have a common property, such as passage through a given line in a given plane. 束一组有共同性质的物体，如一组线等在已知平面上穿过一条已知直线的几何图形
