triangle .. ^^
it is a trigon or as most people call it triangle
A polygon, but only if it has no curves.
This is formed from the ancient Greek words for 20 and 3. It is an Icosikaitrigon
heptagon
Dekagon.
circle
It's called an internally contradictory definition. "Quadrilateral" means a figure with four sides. A figure with no sides is not a quadrilateral.
A polygon.
A quadrilateral.
An octagon.
A decagon.
A hendecagon.