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The 76 pages that link to Circle, each with the reason it gives.

• RadianRelated: Its radius and circumference define how radians measure an angle.

• Conic sectionBroader topic: A plane perpendicular to the cone’s axis can cut a circular section.

• SphereNarrower topic: A circle is the two-dimensional counterpart of a sphere.

• Centripetal forceRelated: Its radius and center define the geometry used to describe centripetal force.

• PolygonCompared with: A circle has a curved boundary, unlike a polygon’s straight sides.

• Angular frequencyRelated: One full revolution supplies the 2π-radian phase change per cycle.

• Analytic geometryBroader topic: The distance formula yields its standard coordinate equation.

• Simply connected spaceCompared with: Its noncontractible loop makes it a basic example that is not simply connected.

• Unit circleNarrower topic: A unit circle is the special case whose fixed distance is one.

• Cyclic quadrilateralNarrower topic: All four vertices must lie on this geometric locus.

• EllipseCompared with: A circle is the limiting symmetric case of an ellipse, with coincident foci.

• HomeomorphismRelated: A circle and the boundary of a square are homeomorphic despite their different outlines.

• PiNarrower topic: Pi is defined by comparing a circle’s circumference with its diameter.

• Synthetic geometryBroader topic: Synthetic arguments often exploit tangency, cyclicity, and equal angles in circle configurations.

• Isoperimetric inequalityBroader topic: It is the unique plane shape attaining equality for fixed perimeter.

• Inscribed angle theoremNarrower topic: The theorem is a basic tool for solving problems about angles on circles.

• Power of a pointNarrower topic: Power is defined relative to a circle and depends on its center and radius.

• RadiusNarrower topic: A radius is defined by its endpoints on this curve and at its center.

• Regular polygonCompared with: As the number of sides grows, suitably scaled regular polygons approximate a circle.

• DiameterNarrower topic: A circle’s center and circumference determine which chords qualify as diameters.

• ManifoldBroader topic: The circle is the simplest compact one-dimensional manifold without boundary.

• Surface areaRelated: Circular regions form the ends of cylinders and contribute to their surface area.

• ParabolaCompared with: Unlike a parabola, a circle has a center and no directrix-based definition.

• IncircleNarrower topic: The incircle is a circle whose fixed radius reaches all three triangle sides.

• MidpointRelated: The midpoint of a diameter is the circle’s center.

• Möbius transformationRelated: Möbius maps carry generalized circles, including lines, to generalized circles.

• PerimeterRelated: Its boundary length is called circumference, the circular counterpart of perimeter.

• Semimajor axisCompared with: A circle has equal semiaxes, so its semimajor axis is simply its radius.

• Cross-ratioRelated: A Möbius transformation maps generalized circles to generalized circles, allowing cross-ratios to test cyclic configurations.

• Polar coordinate systemRelated: A circle centered at the origin is specified by a constant radius.

• Central angleNarrower topic: A central angle is defined by its position within this geometric figure.

• MandalaRelated: Circular boundaries often mark the mandala's sacred enclosure.

• Rotational symmetryBroader topic: Every rotation about its center preserves a circle.

• Thales' theoremRelated: The circle supplies the arc on which the right angle's vertex lies.

• Uniform circular motionNarrower topic: It defines the path whose radius remains fixed throughout the motion.

• Euclidean planeBroader topic: Circles are the basic loci defined by Euclidean distance.

• PendentiveRelated: The dome’s circular base meets the curved surfaces above the square bay.

• TorusRelated: The torus is formed as the product of two circles.

• ChordNarrower topic: A chord is defined by endpoints on this curve.

• Radical axisNarrower topic: The centers and radii of the two circles determine their power functions.

• Brahmagupta's formulaRelated: A cyclic quadrilateral is defined by its vertices lying on one circle.

• Distance formulaRelated: The distance formula tests whether a point lies at a circle’s radius from its center.

• Homotopy equivalenceRelated: It represents the homotopy type of the punctured plane and many annular spaces.

• Isoperimetric problemBroader topic: Among planar closed curves of fixed length, it encloses the greatest area.

• Stereographic projectionRelated: Circles on the sphere project to circles or straight lines in the plane.

• Implicit differentiationBroader topic: Its equation yields tangent slopes without solving separately for the upper and lower semicircles.

• Intersecting chords theoremRelated: The chord endpoints lie on this curve, which supplies the proof’s angle relations.

• Closed curveBroader topic: A circle is a particularly symmetric closed curve, not the general shape of a loop.

• ConeRelated: The cone’s base is circular, and its radius determines the base’s size.

• Hippocrates of ChiosRelated: His construction uses relationships among arcs and areas of circles.