circle
set of all points in a plane that are equidistant from a point called the center
center
the point that all points on a circle are equidistant to
radius
a line segment with one endpoint at the center of a circle or sphere and the other endpoint on the circle or sphere
chord
a line segment with endpoints on a circle
diameter
a line segment that passes through the center of a circle and has both endpoints on that circle
secant
a line in the plane of a circle that intersects the circle at two points
tangent
a line in the plane of a circle that intersects the circle at exactly one point
central angle
an angle whose vertex is the center of a circle and whose rays contain radii of the circle
minor arc
an arc having a measure less than 180 degrees
major arc
an arc having a measure greater than 180 degrees
semicircle
half of a circle; an arc that measures 180 degrees
inscribed
an angle whose vertex is on the circle and whose rays contain chords of the circle
intercepted
an arc on a circle whose points lie between the rays of a given angle
arc
an unbroken part of a circle
circumference
the distance around a circle
circumscribed
a circle that encompasses a polygon and passes through every vertex of that polygon
pi
an irrational number represented by the ratio of the circumference of a circle to the diameter of the circle
point of tangency
the point where a circle and a tangent intersect