Definition:Gnomon

Euclid's Definition
As defined by Euclid:


 * "In any parallelogrammic area let any one whatever of the parallelograms about its diameter with the two complements be called a gnomon."


 * Gnomon.png

Alternatively, it can be intuitively defined as a parallelogram with a similar parallelogram taken out of the corner.

Linguistic Note
The word is a Greek one, generally meaning "marker" (or "a thing that enables something to be known"), and specifically meaning the piece of a sundial that casts the shadow.

The words "gnostic" and "agnostic" come from the same root.

The word is nowadays rarely (if ever) encountered outside the works of Euclid; specifically,.