Circle: the set of all points which are at fixed distance r (the radius) from the center of the circle
Circumference: the length around the circle
Diameter: the distance from one point on a circle through the center to another point on the circle
Distance: a numerical or occasionally qualitative measurement of how far apart objects or points are
Euclidean Geometry: the study of plane and solid figures on the basis of axioms and theorems employed by the Greek mathematician Euclid
Metric Space: a mathematical structure which consists of a set of points and a rule (or function) for measuring distance between any two points in the set
Non-Eculidean Geometry: any geometry that is not the same as Euclidean geometry
π (Pi): the ratio of the circumference of a circle to its diameter.
Taxicab Circle: the concept of a circle and its definition within the Taxicab metric system
Taxicab Distance (metric): the distance between two points measured as the sum of the change in horizontal and vertical directions between the two points
