There is none. If this was a question on a test or quiz, the answer was probably point, though that is technically incorrect.
Quadrilateral is the name fr a geometric figure with 4 sides.
Circle has no vertex, sides
An hexagon is polygon that has 6 sides
thirtyagon
quadrilateral
Decagon
Octagon
A circle with any radius, including zero.
0
dodecagon
a pentadecagon
An octagon.