An example of something that is perpendicular is a light post that is standing upright next to a street.
In most houses, the walls are perpendicular to the floor.
Origin of perpendicular
- Middle English perpendiculer from Old French from Latin perpendiculāris from perpendiculum plumb line from perpendere to weigh carefully per- per- pendere to weigh (s)pen- in Indo-European roots
From American Heritage Dictionary of the English Language, 5th Edition
- Latin perpendiculum (“plumb line").