GNOMON

gnomon

(noun) indicator provided by the stationary arm whose shadow indicates the time on the sundial

Source: WordNet® 3.1

Etymology

Noun

gnomon (plural gnomons)

An object such as a pillar or a rod that is used to tell time by the shadow it casts when the sun shines on it, especially the pointer on a sundial. [from mid 16th c.]

Synonyms: cock, style

An object such as a pillar used by an observer to calculate the meridian altitude of the sun (that is, the altitude of the sun when it reaches the observer's meridian), for the purpose of determining the observer's latitude.

The index of the hour circle of a globe.

(geometry) A plane figure formed by removing a parallelogram from a corner of a larger parallelogram.

(mathematics, by extension) A number representing the increment between two figurate numbers.

Source: Wiktionary

Gno"mon, n. Etym: [L. gnomon, Gr. Gnome.]

1. (Dialing)

Definition: The style or pin, which by its shadow, shows the hour of the day. It is usually set parallel to the earth's axis.

2. (Astron.)

Definition: A style or column erected perpendicularly to the horizon, formerly used in astronomocal observations. Its principal use was to find the altitude of the sun by measuring the length of its shadow.

3. (Geom.)

Definition: The space included between the boundary lines of two similar parallelograms, the one within the other, with an angle in common; as, the gnomon bcdefg of the parallelograms ac and af. The parallelogram bf is the complement of the parallelogram df.

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

Source: Webster’s Unabridged Dictionary 1913 Edition