| A | B |
|---|
| unit circle | a circle with a radius of one |
| arc of a circle | two points on a circle and the continuous part of the circle between those points |
| central angle | the angle formed by two radii |
| chord of a circle | a segment whose endpoints lie on the circle |
| circle | the set of all points in a plane at a given distance at a given point |
| concentric circles | coplanar circles that share the same center |
| diameter of a circle | a chord which contains the center of a circle, or the length of that chord |
| inscribed angle | an angle formed by two chords with a common endpoint |
| intercepted arc | an arc whose endpoints are part of different sides of an angle |
| major arc of a circle | an arc of a circle whose measure is greater than 180 degrees |
| minor arc of a circle | an arc of a circle whose measure is less than 180 degrees |
| point of tangency | the one point at which a tangent touches the circle |
| radius | a segment from the center of a circle to a point on the circle, or the length of the segment |
| secant of a circle | a line which contains a chord |
| semicircle | an arc of a circle with a measure of 180 degrees |
| tangent to a circle | a line that lies in the plane of a circle and intersects the circle at exactly one point |
| cyclic quadrilateral | a quadrilateral that is inscribed in a circle |
| circumference | the distance around a circle |
| angular velocity | the change in the central angle over time as an object moves along a circular path |
