- 铅垂线 qiānchuíxiàn plumb line; sounding line; lead lineWeighted line used to determine verticality or to measure the depth of water in navigation
- 公垂线 gōngchuíxiàn common perpendicularA straight line that intersects two other lines at right angles
- 垂线足 chuíxiànzú foot of a perpendicularthe point where a line meets another line or a plane at a right angle