ECB Junior is having his first lessons in geometry and has come home having to explain various terms to me.

We are struggling with the difference between Lotrecht and Senkrecht. He can explain them to me but our German/English dictionary translates both as being perpendicular .. which his explanations do not tally with.

Any help anyone?

" Lotrecht and Senkrecht"

google translate told me it was "Perpendicular and Vertical"

Lotrechte is the (colloquial?) Senkrechte. But AFAIK the Lotrechte is always senkrecht (90 degree angle) to a horizontal line.
"senkrecht" describes the relation between two lines (90 degree angle) regardless of their position (don't have to be lotrecht/horizontal).

maybe you were just looking for the english terminology (?) or maybe I got it all wrong...bump

Well after his lesson today, my son was telling me that senkrecht is always square on to a line (he has not learnt about degrees and angles but what he was showing me was that it always has to be at right angles to a line) whereas lotrecht is upright.

The example he was given was that a chimney is lotrecht to a sloping roof - if it was senkrecht, it would be at a funny angle. So I understand senkrecht to be perpendicular and lotrecht to be vertical - but my very big and usually very reliable dictionnary gave perpendicular for both.

It seems strange to me, that the term "lotrecht" is used in the context of maths (where normally "rechtwinklig" or "orthogonal" would be used).

A "Lot" is a tool which is mostly used to determine wheter a wall is pependicular to the ground or not. In its simplest form it is just a string which a weight attached. "Lotrecht" litterally means the direction into which the Lot is pointing (i.e. the direction of gravity.)https://de.wikipedia.org/wiki/Lotrechte
According to wikipedia the corresponding English term is vertical direction.

It seems though that in Geometry the therm Lot is used (altougth I never heard it in this context before). In which case it just means a line which is perpendicular to an other line.https://de.wikipedia.org/wiki/Lot_(Mathematik)

The term Senkrecht is a bit ambigious it is actually synonymos to "Lotrecht" (it derived from the word "Senkblei" which is onother word for "Lot") and means the vertical direction. But it is on the same time often used to express that two lines are perpendicular to each other (here "rechtwinklig" or "orthogonal" would be better choices). It seems as if the teacher did not pick the best termology.