KnowraDiameterDiameterA diameter is a chord of a circle that passes through its center. Its length is twice the radius.BriefConnectRadius: A line segment from a circle’s center to a point on its circumference. A diameter consists of two radii joined end to end through the center.Pi: The mathematical constant equal to the ratio of a circle’s circumference to its diameter. Multiplying the diameter by π gives the circle’s circumference.Circumference measurement: The determination of a circle’s perimeter from direct measurement or geometric relationships. A measured diameter provides the circumference through multiplication by π.Radius of gyration: A distance that represents how a body’s mass or area is distributed around an axis. Unlike a circle’s radius, it summarizes a distribution and need not reach a boundary.Chord: A line segment joining two points on a curve or geometric figure. A diameter is the special chord that passes through the circle’s center.Area of a circle: The measure of the region enclosed by a circle, equal to π times the radius squared. Substituting half the diameter for the radius expresses area directly in terms of diameter.Telescope aperture: The diameter of a telescope’s light-collecting opening. Aperture diameter determines how much light a telescope can collect.Circumradius: The radius of a circle passing through all vertices of a polygon. A circumradius is half the diameter only when the enclosing circle is specified.Circle: The set of points in a plane at a fixed distance from a central point. A circle’s center and circumference determine which chords qualify as diameters.Thales' theorem: A theorem stating that an angle inscribed in a semicircle is a right angle. A diameter forms the side opposite the right angle in every such inscribed triangle.Show all 20Linked from 17 pagesHausdorff dimensionRelated: Covering sets are weighted by powers of their diameters in the Hausdorff construction.Borsuk's conjectureNarrower topic: The conjecture compares each part’s diameter directly with that of the original set.PerimeterCompared with: Diameter is a straight-line dimension, whereas circumference runs around the circle.Bounded setRelated: A nonempty set is bounded exactly when its diameter is finite.SemiperimeterCompared with: Though both quantities can be half of a larger measure, diameter halves a circle’s width, not a polygon’s perimeter.Law of sinesRelated: The common side-to-sine ratio equals the circumcircle’s diameter.Barbier's theoremCompared with: A constant-width curve has fixed directional widths, a condition stronger than fixed diameter.Planetary radiusRelated: A diameter spans the full body and equals twice a spherical radius.Show all 17