Why is a circle round and not elliptical?

A circle is a closed curved shape that is flat. In a circle, all points on the circle are equally far from the center of the circle. An ellipse is also a closed curved shape that is flat. Instead of having all points the same distance from the center point, though, an ellipse is shaped so that when you add together the distances from two points inside the ellipse they always add up to the same number.