垂直線(すいちょくせん)

Composed of 垂直(すいちょく) (vertical; perpendicular) and 線(せん) (line). The meaning depends on context: in everyday usage it typically means 'vertical line' (running up-and-down on the page); in geometry, it refers to a line that is perpendicular to a given line or surface, regardless of its absolute orientation.

Usage

Two main contexts

• **Everyday / visual**: a line that stands upright on the page or screen, contrasting with 水平線(すいへいせん) (horizontal line).
• **Mathematics / physics**: a line that meets another line or plane at a 90-degree angle.

Common collocations

• 垂直線(すいちょくせん)を引(ひ)く: to draw a vertical / perpendicular line
• 垂直線(すいちょくせん)を下(お)ろす: to drop a perpendicular (from a point to a line or plane)
• 垂直線(すいちょくせん)と水平線(すいへいせん): vertical and horizontal lines
• 垂直線(すいちょくせん)に対(たい)して: with respect to the vertical / perpendicular line

Similar words

• 水平線(すいへいせん): horizontal line — the natural antonym
• 垂線(すいせん): perpendicular (line) — a shorter, more formal geometric term, particularly common in math textbooks
• 直線(ちょくせん): straight line — the general term for any straight line, regardless of orientation
• 縦(たて)線(せん): vertical stroke / line — more informal; often used in everyday descriptions of patterns and drawings
• 鉛直線(えんちょくせん): plumb line — a physical line hanging straight down under gravity; used in surveying and physics for true verticality