the set of all points in a plane that are equidistant (the length of the radius) from a given point called the center

a segment in the interior of a circle whose endpoints are on the circle

a segment between two points on a circle passing through the center of the circle. 

a line that intersects a circle at two points on the circle

a line that intersects the circle at exactly one point

If a line is tangent to a circle then the line is perpendicular to a radius of the circle drawn to the point of tangency.

If two segments are tangent to a circle from the same external point, then they are congruent.

a connected section of the circumference of a circle; has a linear measurement and a degree measurement.

shorter of the two arcs; < 180^o

larger of the two arcs: > 180^o

an arc that measures 180^o

the region of a circle formed by a central angle and its intercepted arc.

an angle whose vertex is the center of the circle

an angle whose vertex lies on the circle and whose sides are chords of the circle.

formed when segments intersect portions of a circle

the set of all points in space that are equidistant from a center point.

the degree measure of an arc; equal to the central angle that intercepts it