• ### Arc

Two endpoints on a circle and all of the points on the circle between those two endpoints.

• ### Center

The point from which all points on a circle are equidistant.

• ### Central Angle

An angle whose vertex is the center of a circle.

• ### Chord

A segment whose endpoints are on a circle.

• ### Circle

A geometric figure composed of points that are equidistant from a given point.

• ### Circle Segment

The region within a circle bounded by a chord of that circle and the minor arc whose endpoints are the same as those of the chord.

• ### Circumscribed Polygon

A polygon whose segments are tangent to a circle.

• ### Concentric Circles

Circles that share a center.

• ### Diameter

A chord that intersects with the center of a circle.

• ### Equidistant

The same distance. Objects can be equidistant from one another.

• ### Inscribed Polygon

A polygon whose vertices intersect with a circle.

• ### Major Arc

An arc greater than 180 degrees.

• ### Minor Arc

An arc less than 180 degrees.

• ### Point of Tangency

The point of intersection between a circle and its tangent line or tangent segment.

A segment with one endpoint at the center of a circle and the other endpoint on the circle.

• ### Secant Line

A line that intersects with a circle at two points.

• ### Sectors

A region inside a circle bounded by a central angle and the minor arc whose endpoints intersect with the rays that compose the central angle.

• ### Semicircle

A 180 degree arc.

• ### Tangent Line

A line that intersects with a circle at only one point (the point of tangency).

• ### Tangent Segment

A segment with one endpoint at the point of tangency of a circle and the other endpoint on the tangent line.