Circle Geometry
Study circle parts, circle lines, circle regions, and circle-angle relationships with dedicated interactive pages.
15 concepts in this topic
This category keeps the whole circle system together, from radius and diameter to tangents, arcs, sectors, and angle relationships, so the topic feels connected instead of fragmented.
Center
The center is the point equally distant from every point on the circle.
Radius
A radius is a segment from the center of a circle to a point on the circle.
Diameter
A diameter is a chord passing through the center and equals two radii.
Circumference
The circumference is the distance around the circle.
Chord
A chord is a segment with both endpoints on the circle.
Secant
A secant is a line that passes through a circle at two points.
Tangent
A tangent touches a circle at exactly one point.
Arc
An arc is a portion of a circle's circumference.
Semicircle
A semicircle is half of a circle and spans 180 degrees.
Sector
A sector is the region bounded by two radii and the included arc.
Segment
A circle segment is the region between a chord and its arc.
Annulus
An annulus is the ring-shaped region between two concentric circles.
Central Angle
A central angle has its vertex at the center of the circle.
Inscribed Angle
An inscribed angle has its vertex on the circle and intercepts an arc.
Tangent-Chord Angle
A tangent-chord angle is formed by a tangent and a chord through the point of tangency.