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Definition: radius from The Hutchinson Unabridged Encyclopedia with Atlas and Weather Guide

Straight line from the centre of a circle to its circumference, or from the centre to the surface of a sphere.


Circles: working out area, diameter and radius



Summary Article: radius
from The Chambers Dictionary

(pl radii /rā'di-ī/ or ra'diuses) a straight line from the centre to the circumference of a circle or surface of a sphere (geom); a radiating line; anything placed like a radius, such as the spoke of a wheel, the movable arm of a sextant, etc; a radial plane of symmetry in a coelenterate; a line from a fixed point (eg the focus of a conic) to a point on a curve; the outer bone (in supine position) of the forearm in humans, or its equivalent in other animals; a barbule of a feather; the third vein of an insect's wing; a ray-flower or the ray-flowers of a head collectively (rare); a distance from a centre, conceived as limiting an area or range. [L radius a rod, spoke, ray]

■ ra'dial

see separate entry.

❑ radius of curvature

(geom) of any curve, the radius of the circle which can be superimposed on it on the concave side.

❑ radius vector

(pl radii vectō'res /-rēz/) a straight line joining a fixed point and a variable point.

© 2015 by Chambers Publishing Ltd.

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