[chuí zhí]
perpendicular; vertical; squareness; verticality; perpendicularity
The two lines meet at right angles.
两线垂直相交。
Let AB be perpendicular to CD.
设 AB 垂直于CD。
When a surface is perpendicular to the rays, their intensity is at its maximum.
当表面与射线垂直时，射线的强度最大。