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Circle

A shape consisting of those points in a plane which are equidistant from a given point called the center.

Pi (π)

The ratio of the circumference to the diameter of a circle.

Radius

A line from the center of the circle of the circle to any point on the circle.

Radii

more than 1 radius.

Chord

A line segment that links 2 points on a circle.

Diameter

A chord that crosses through the center of the circle.

Tangent

A line or ray that interests a circle at only 1 point.

Point of Tangency

The point where a circle and a tangent intersect.

Arc

Part of a circle with an angle measure.

Minor Arc

Arc whose measure is smaller than 180 degrees.

Major Arc

Arc whose measures is larger than 180 degrees.

Semi-circle

Arc whose measure is equal to 180 degrees.

Central Angle

An angle whose vertex is a center of a circle.

Congruent Circles

Circles with congruent radii.