Regular Pentagon

I’m reviewing math lessons with Vian before his test. We’re on a chapter about polygons.

  Me: What is a pentagon? 
Vian: It's a polygon with five sides. 
  Me: Good! What is a regular pentagon? 
Vian: A regular pentagon? 
  Me: Yeah.
Vian: I think it is a pentagon that is not special? 
  Me: What?
Vian: It's a pentagon without anything special about it. Just regular.
  Me: *laughing* It's a pentagon with equal sides.
Vian: Oh!

Needless to say he will be retaking his test tomorrow.