from The Century Dictionary and Cyclopedia
- n. On a sun-dial, the triangular projecting piece which by its shadow shows the hour of the day; also, any index to a sun-dial or to a meridian-mark, especially a very large one. The early gnomons used for astronomical purposes were vertical pillars or obelisks.
- n. The index of the hour-circle of a globe.
- n. A piece of a parallelogram left after a similar parallelogram has been removed from a corner of it. Thus, in the figure, EFGBCD is a gnomon.
- n. An odd number; one of the terms of an arithmetical series by which polygonal numbers are found. Also called gnomonic number.
It had always sounded strangely in my ears, like the word gnomon in the Euclid and the word simony in the Catechism.
We saw that Thales made some remarkable measurements with the aid of shadows, and we have more than once referred to the gnomon, which is the most primitive, but which long remained the most important, of astronomical instruments.
There will be a roof garden that will form a giant sundial, with Wren's 202ft column acting as the gnomon, the pillar which creates a shadow on the dial, indicating the time across the landscaping.
'Gnomon' comes from the Greek 'gignoskein,' to know.