Illustration of gnomon
- bcdefg gnomon 2
gnomon
noun
gno·mon ˈnō-mən 
-ˌmän
1
: an object that by the position or length of its shadow serves as an indicator especially of the hour of the day: such as
a
: the pin of a sundial
b
: a column or shaft erected perpendicular to the horizon
2
: the remainder of a parallelogram after the removal of a similar parallelogram containing one of its corners
Example Sentences
Recent Examples on the Web The gnomon, or the shadow-casting protrusion, is 35 feet tall with a shadow twice that length. 
Stefanie Waldek, Travel + Leisure, 15 Nov. 2021 But the most original marketing device was a giant sundial, its vertical monument (called a gnomon) 28 feet long and 17 feet high and standing in a circle 34 feet in diameter. Gary Kamiya, San Francisco Chronicle, 9 July 2021 The pole serves as a gnomon, the part of a sundial that casts a shadow to denote time. Jeanne Huber, Washington Post, 20 Apr. 2020 There are many types of sundials, but in general each consists of a gnomon, a thin rod that casts a shadow onto a dial, and a flat plate or platform. Megan Arnett, Scientific American, 15 Mar. 2018 The original clock is missing its gnomon, the part of a sundial that casts a shadow, but an 18th-century museum curator described it having one in the shape of a pig’s tail, so Parslow re-created that, too. National Geographic, 19 Jan. 2017
Stefanie Waldek, Travel + Leisure, 15 Nov. 2021 But the most original marketing device was a giant sundial, its vertical monument (called a gnomon) 28 feet long and 17 feet high and standing in a circle 34 feet in diameter. Gary Kamiya, San Francisco Chronicle, 9 July 2021 The pole serves as a gnomon, the part of a sundial that casts a shadow to denote time. Jeanne Huber, Washington Post, 20 Apr. 2020 There are many types of sundials, but in general each consists of a gnomon, a thin rod that casts a shadow onto a dial, and a flat plate or platform. Megan Arnett, Scientific American, 15 Mar. 2018 The original clock is missing its gnomon, the part of a sundial that casts a shadow, but an 18th-century museum curator described it having one in the shape of a pig’s tail, so Parslow re-created that, too. National Geographic, 19 Jan. 2017 Word History
Etymology
borrowed from Latin gnōmōn "pointer of a sundial," borrowed from Greek gnṓmōn "examiner, interpreter, carpenter's square, pointer of a sundial," from gnō-, base of gignṓskein "to perceive, know" + -mon-, -mōn, agent suffix — more at know entry 1
First Known Use
1546, in the meaning defined at sense 1