Circumferences are flat geometric figures usually represented by “perfectly round” figures, but the geometric representation is nothing more than the representation of an algebraic formula. Circumferences are defined based on sets of points and their geometric representations are based on these definitions.
Another way to refer to circumferences is to use the terms "all the way around, arc-lengthwise". The important thing to remember is that the circumference is a geometric figure belonging to the plane that is made up of all points equally distant from a fixed point of that plane.
