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 be constructed on a sphere as a pair of 180 degree arcs connecting antipodal points, when it forms a lune.

When higher-dimensional polytopes involving squares or other tetragonal figures are alternated, these digons are usually discarded and considered single edges.

A second visual representation, infinite in size, is as two parallel lines stretching to (and projectively meeting at; i.e. having vertices at) infinity, arising when the shortest distance between the two edges is greater than zero.

Any straight-sided digon is regular even though it is degenerate, because its two edges are the same length and its two angles are equal (both being zero degrees).