Circles

CIRCLE A circle is the set of all points in a plane that are a fixed distance from a point called the center of the circle.

RADIUS A radius of a circle is a line segment joining the center of the circle to one of the points on the circle.

DIAMETER A diameter of a circle is a line segment that contains the center of the circle and has its endpoints on the circle.

TANGENT A tangent to a circle is a line that intersects the circle in exactly one point. The point is called the point of the tangent.

CHORD A chord is a line segment with endpoints on the circle.

ARC An arc of a circle is an unbroken portion of the circle.