鉛えん直ちょく線せん

noun

vertical line; plumb line

Technical term in geometry, physics, and engineering for a line that is exactly vertical, often defined by gravity or a plumb bob.

• 鉛えん直ちょく線せんに対たいして直ちょっ角かくな線せんを水すい平へい線せんという。

  A line at a right angle to a vertical line is called a horizontal line.

• 建たて物ものの傾かたむきを測はかるために鉛えん直ちょく線せんを引ひく。

  Draw a vertical line to measure the tilt of the building.