What is a 99 sided polygon called?

Answer 1

The proposed name for a nine sided polygon is Nonagon or Enneagon. If you were going to talk about a 99 sided polygon then you would call it an Enneacontakaienneagon. Polygons are a plane figure where each line segment touch each other but do not cross each other.

Answer 2

There is no assigned name, but names for polygons use Greek prefixes, so using the prefix for 90 (enneaconta) and for 9 (ennea), it would be an enneacontakaienneagon or enneacontaenneagon.

(An alternate name could be nonacontanonagon, using the alkene protocol of units followed by tens, and the Latin prefix nona-.)