[mjp]

triangle = 3 sides
rectangle = 4 sides
pentagon = 5 sides
hexagon = 6 sides
number of sides approaches infinity
circle = infinite sides

[where's_the_Outrage?]

Interesting, reminds me of calculus using the differential from zero to infinity.

so taking that one step further (or rather to the beginning) you would start:

point = 0 sides
line = 2 sides

[gundog]

Infinite points in the perimeter. As it takes two points to define a line, or side, I would say zero sides. There are no flat spots on the perimeter.