In another forum in a discussion regarding a traffic intersection, someone posted this comment:

“...it looks like a distinction between English english and American English.  In the former perpendicular means at 90 degrees to the ground, vertical - hard going for any cab.”

Is this statement correct in regards to English english, i.e., does perpendicular only mean at 90 degrees to the ground?  (The individual who posted it implied that in England, one would never say “road x runs perpendicular to road y”.  That only Americans say this.)

The ADH says perpendicular means 1) “intersecting or forming right angles” 2) “right angle to the horizontal or vertical”.  So both of the meanings are acceptable in the US.  What about elsewhere in the English speaking world?  Are both of these meanings used or just #2? 

(ADH gives the origin as Lat. perpendiculum:  plumb line)

Perpendicular _can_ mean perpendicular to the ground in British English, but it can also mean perpendicular to any other specified plane or line.

The OED marks the definition of being at right angles to any given plane as being “chiefly Science and Engin.” All the other definitions are specifically vertical in nature.

The slang senses like “to remain perpendicular” meaning to remain standing and/or sober are also used in Leftpondia.

Perpendicular _can_ mean perpendicular to the ground in British English, but it can also mean perpendicular to any other specified plane or line.

But it’s my feeling that - outside geometry, draughtsmanship or other technical contexts - it usually doesn’t. I use it as a synonym, more or less, for vertical or upright; I would never say “road x runs perpendicular to road y” and would be quite surprised to hear anyone else say it.

Very well then. I hear from a lot of chiefly Science and Engin people.

Even in the context of 2-dimensional geometry, perpendicular retains a faint hint of verticalness to it. In geometrical construction, one often speaks of ‘erecting a perpendicular’ or ‘dropping a perpendicular’, even id the resulting line isn’t straight up and down the page.

Here’s an interesting combination of the two at algebra.com

Question 208037: A car is traveling on a road that is perpendicular to a railroad track. when the car is 30 meters from the crossing, the car’s collision detector warns that there is a train 50 meters from the car and heading toward the same crossing. How far is the train from the crossing?

This is news to me, so I’ll ask the obvious question: is there a preferred word for “intersecting at right angles” in British English?  Surely it’s not orthogonal.

Come to think of it, with all the roundabouts, maybe it just never comes up.

How far is the train from the crossing?

40 meters. I think it’s fun that it doesn’t matter if the car is perpendicular to the ground or not. It’s a valid math problem with the same answer either way.

"Road x is perpendicular to road y” sounds odd to me. Other than in Euclidean geometry (where I was taught that “perpendicular to” means “at right angles to"), the implication of “perpendicular” in real life has always been for me “vertical”, i.e. “perpendicular to the ground”. I would have said “road x runs at right angles to road y”. My education (such as it was) has had a rightpondian bias.

From Wikipedia:

The Perpendicular Gothic period (or simply Perpendicular) is the third historical division of English Gothic architecture, and is so-called because it is characterised by an emphasis on vertical lines.

Why “vertical” should imply “perpendicular to the ground” is, however, beyond me. I’m sure there’s a reason.

lionello - 12 December 2012 07:19 PM

Why “vertical” should imply “perpendicular to the ground” is, however, beyond me. I’m sure there’s a reason.

If horizontal is “parallel to the horizon” and vertical is perpend*ahem* at right angles to horizontal, then...it kinda has to.

NotThatGuy: perhaps lionello lives in a hilly area…

Not at all. The highest point in my home town (where the water tower stands) is 40 m above sea level. The area used to be a swamp......"A hill there is, a little to the North, and to its purpledicular top a narrow way leads forth” (E. Lear, The Two Old Bachelors)

I suppose too much of my time is spent horizontal. It’s probably the vodka.

NotThatGuy - 12 December 2012 04:16 PM

This is news to me, so I’ll ask the obvious question: is there a preferred word for “intersecting at right angles” in British English?  Surely it’s not orthogonal.

No, we just say ‘at right angles’.

Okay, lionello, the point I was making to NTG is that vertical is only at right angles to the ground when the ground is horizontal…