- A minusagon is a value that when added to a polygon, removes one or more sides from that polygon. Compare with a plusagon, which adds a side. Some mathematicians argue that minusagons and plusagons are the same type of object. Others argue they don’t exist.
- The Light Fantastic (allthetropes.org)
The second Discworld novel, from 1986. A direct sequel to The Colour of Magic, it opens with the Octavo changing the whole world to save Rincewind and Twoflower from falling off the Disc at the end of that book. From then on, they struggle to get back to Ankh-Morpork as there are power struggles in Unseen University and the world turtle heads inexorably towards a great red star that threatens to strip away the Discworld’s magical field.
- Digon (Wikipedia)
In geometry, a bigon, digon, or a 2-gon, is a polygon with two sides (edges) and two vertices. Its construction is degenerate in a Euclidean plane because either the two sides would coincide or one or both would have to be curved; however, it can be easily visualised in elliptic space. It may also be viewed as a representation of a graph with two vertices, see “Generalized polygon”.