A Circle SVG is a geometric place of points in the plane, the distance from which to a given point, called the center of the circle, does not exceed a given non-negative number, called the radius of the circle. If the radius is zero, the circle degenerates to a point.
At unstrict (≤) inequality the definition of the closed circle turns out. Boundary of a circle by definition is a circle.
Circle SVG Related definitions
Radius is the segment connecting the center of the circle with its border.
Diameter – a segment that connects the two points of the circle boundary and contains its center.
The sector of the circle is the intersection of the circle and its central corner, i.e. the part of the circle bounded by an arc and two radii connecting the ends of the arc with the center of the circle.
A segment is a part of a circle bounded by an arc and a chord that pulls it together.
These and other elements of the circle, as well as the relations between them, are described in the article The Circle.
The chord is a segment connecting any two points of the circle.