Gnō'mon, n.

(nō'mon), n. [Gr. γνώμων, one that knows, the index of a sun-dial, Lat. gnomon. See GNOME.]

1. (Dialing.) The style or pin, which, by its shadow, shows the hour of the day. Brande.
2. (Astron.) A style or column erected perpendicularly to the horizon, and formerly used for making astronomical observations. Its principal use was to find the altitude of the sun by measuring the length of its shadow.
3. (Geom.) The space included between the boundary lines of two similar parallelograms, the one within the other, with an angle in common; as the gnomon b c d e f g of the parallelogram a c and a f.

Gnomon. 4. The index of the hour-circle of a globe.