Interior of a circle Any point on the inside of a circle.

(black is the interior of a circle)

Exterior of a circle Any points on the outside of a circle.

(purple is the exterior of the circle)

Central AngleAn angle that intersects a circle in two points and has its vertex at the center of the circle.

ArcA part of a circle that is defined by two endpoints.

Minor ArcAn arc with a measure less than 180 degrees.

Major ArcAn arc with a measure greater than 180 degrees.

Circumscribed A circle around all four vertices of a polygon.

Inscribed A circle on the inside of a square touching each side once.

Pi An irrational number represented by the ratio of the circumference of a circle to the diameter of the circle: Pi= circumference/diameter.

Tangent (Point of Tangency)A line in the plane of a circle that intersects the circle in exactly one point. The point of intersection is called the point of tangency.

CircumferenceDistance around a circle: Circumference=diameter(pi).

- Interior of a circle Any point on the inside of a circle.

(black is the interior of a circle)- Exterior of a circle Any points on the outside of a circle.

(purple is the exterior of the circle)