The New International Encyclopædia/Diameter

​DIAM′ETER (Lat. diametros, from Gk. διάμετρος, diameter, from διά, dia, through + μέτρον, metron, measure). A diameter of a conic section (q.v.) is any chord which connects the points of contact of parallel tangents. In the circle, ellipse, and hyperbola, all diameters pass through the centre (see Curves) and are bisected by it. Only the circle has all diameters equal, and each bisects the chords perpendicular to it. In the ellipse only the diameters called the minor and major axis bisect the chords perpendicular to them. In the parabola all diameters are parallel to the axis. (For conjugate diameters, see Conjugate.) Certain solid bodies also have diameters. In the sphere and the ellipsoid, the lines passing through the centre are called diameters and are bisected by the centre. See Axis.

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