Is It Undecagon or Hendecagon?

A hendecagon is an 11-sided polygon, also variously known as an undecagon or unidecagon. The term "hendecagon" is preferable to the other two since it uses the Greek prefix and suffix instead of mixing a Roman prefix and Greek suffix.

Is there a shape called a hendecagon?

In geometry, a hendecagon (also undecagon or endecagon) or 11-gon is an eleven-sided polygon.

What is an eleven-sided polygon called?

In geometry, a hendecagon (also undecagon or endecagon) or 11-gon is an eleven-sided polygon. (The name hendecagon, from Greek hendeka "eleven" and –gon "corner", is often preferred to the hybrid undecagon, whose first part is formed from Latin undecim "eleven".)