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A digon has two sides. It is a polygon in the mathematics of geometry. A digon also has two vertices.
Yes. A digon can have 2 sides, but only in a spherical geometry. In normal Euclidean geometry both the monogon and the digon have just 1 side.
No.
A 2 sided shape is called a digon
a one sided shape is called a henagon and a 2 sided shape is called a digon