All the edges of a regular polygon have the same length, and all the angles are congruent.
If a regular polygon has n edges, it is an n-gon.
By an earlier formula,
each interior angle measures 180×(n-2)/n.
This approaches 180 for large n, but never equals 180.
Therefore the shape is convex.
Starting with 3 edges, the first few n-gons are as follows: