Perpendicular means “meeting at a right angle.”

Quick Scoop: What does perpendicular mean?

  • Two lines (or surfaces) are perpendicular if they intersect to form a 90° angle, also called a right angle.
  • The classic picture is a perfect “L” or “T” shape where the corner is a square corner.
  • The symbol for “is perpendicular to” in math is ⊥\perp ⊥, for example AB⊥CDAB\perp CDAB⊥CD means line AB is perpendicular to line CD.

Simple examples

  • The corner of a sheet of paper: each side meets the other at 90°, so the edges are perpendicular.
  • A person standing upright on flat ground: the body is (approximately) perpendicular to the ground.
  • On a map or compass, north–south and east–west directions are perpendicular.

If two straight lines cross and make a sharp “square corner,” they are perpendicular; if the corner is wider or narrower than a square corner, they are not perpendicular.

TL;DR: Perpendicular = crossing at a right angle (90°), often written with the symbol ⊥\perp ⊥.

Information gathered from public forums or data available on the internet and portrayed here.