radius

[ rey-dee-uh s ]
/ ˈreɪ di əs /

noun, plural ra·di·i [rey-dee-ahy] /ˈreɪ diˌaɪ/, ra·di·us·es.

Origin of radius

1590–1600; < Latin: staff, rod, spoke, beam, orig., ray1
Can be confusedcircumference diameter radius tangent
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

Examples from the Web for radius

British Dictionary definitions for radius

radius

/ (ˈreɪdɪəs) /

noun plural -dii (-dɪˌaɪ) or -diuses

Word Origin for radius

C16: from Latin: rod, ray, spoke
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Word Origin and History for radius

radius


n.

1590s, "cross-shaft," from Latin radius "staff, stake, rod; spoke of a wheel; ray of light, beam of light; radius of a circle," of unknown origin. Perhaps related to radix "root," but Tucker suggests connection to Sanskrit vardhate "rises, makes grow," via root *neredh- "rise, out, extend forth;" or else Greek ardis "sharp point."

The geometric sense first recorded 1610s. Plural is radii. Meaning "circular area of defined distance around some place" is attested from 1953. Meaning "shorter bone of the forearm" is from 1610s in English (the Latin word had been used thus by the Romans).

Online Etymology Dictionary, © 2010 Douglas Harper

Medicine definitions for radius

radius

[ rādē-əs ]

n. pl. ra•di•us•es

A line segment that joins the center of a circle with any point on its circumference.
A long, prismatic, slightly curved bone, the shorter and thicker of the two forearm bones, located laterally to the ulna.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.

Science definitions for radius

radius

[ rādē-əs ]

Plural radii (dē-ī′) radiuses

A line segment that joins the center of a circle or sphere with any point on the circumference of the circle or the surface of the sphere. It is half the length of the diameter.
The shorter and thicker of the two bones of the forearm or the lower portion of the foreleg. See more at skeleton.
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.