I was thumbing through the archive, and found someone asking for the name of a 13 sided shape . Though this article is from Sep. 88’, 7 months after I was born, I wanted to shed more light.
I saw the “freelance” attempt at naming it and thought to myself. I distinctly remember in Trig, we had a primer chapter at the beginning of the book that said after “do decagon”(sp?), all shapes should be referred to as “n-gon”, n simply being the number of sides. Though this may simply be so you don’t spend an extra year in school memorizing what a tetracontakaienneagon(49 sides).
The following site as the whole system and the explanation.
I believe its interchangeable, and that everyone will know what you mean if you say a 21-agon instead of icosikaihenagon or icosihenagon. I see it much like the binomial nomenclature we all learned about in bio. You say thats a Ground Hog, I say its a wood chuck, he says its a marmot, but its really a Marmota monax.
In other words, yes there is a name for all shapes with multiple sides, but who really cares?
(Apparently I do, because that article is almost old enough to drink.)