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radii

[rey-dee-ahy] /ˈreɪ diˌaɪ/
noun
1.
a plural of radius.

radius

[rey-dee-uh s] /ˈreɪ di əs/
noun, plural radii
[rey-dee-ahy] /ˈreɪ diˌaɪ/ (Show IPA),
radiuses.
1.
a straight line extending from the center of a circle or sphere to the circumference or surface:
The radius of a circle is half the diameter.
2.
the length of such a line.
3.
any radial or radiating part.
4.
a circular area having an extent determined by the length of the radius from a given or specified central point:
every house within a radius of 50 miles.
5.
a field or range of operation or influence.
6.
extent of possible operation, travel, etc., as under a single supply of fuel:
the flying radius of an airplane.
7.
Anatomy. the bone of the forearm on the thumb side.
Compare ulna (def 1).
8.
Zoology. a corresponding bone in the forelimb of other vertebrates.
9.
Machinery Now Rare. the throw of an eccentric wheel or cam.
10.
a rounded corner or edge on a machined or cast piece of metal.
11.
Entomology. one of the principal longitudinal veins in the anterior portion of the wing of an insect.
Origin
1590-1600
1590-1600; < Latin: staff, rod, spoke, beam, orig., ray1
Can be confused
Dictionary.com Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2014.
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Examples from the web for radii
  • The latest wind radii and warnings are plotted graphically here.
  • The problem is that different parts of the skater are moving in circles of different radii.
  • Supergiants may have radii a thousand times larger than that of our own sun.
  • Comparing the actual volumes leads you to compare radii cubed.
  • Why are the noble gases' atomic radii so much bigger than the rest of their row.
  • Tropical cyclone wind radii estimation using an empirical inland decay model.
  • The maneuvering radii are of questionable validity, especially during strong low-level wind conditions.
  • Though their radii are in the same direction, they are of different values.
  • The charts shall contain a full range of load ratings at all stated operating radii.
British Dictionary definitions for radii

radii

/ˈreɪdɪˌaɪ/
noun
1.
a plural of radius

radius

/ˈreɪdɪəs/
noun (pl) -dii (-dɪˌaɪ), -diuses
1.
a straight line joining the centre of a circle or sphere to any point on the circumference or surface
2.
the length of this line, usually denoted by the symbol r
3.
the distance from the centre of a regular polygon to a vertex (long radius) or the perpendicular distance to a side (short radius)
4.
(anatomy) the outer and slightly shorter of the two bones of the human forearm, extending from the elbow to the wrist
5.
a corresponding bone in other vertebrates
6.
any of the veins of an insect's wing
7.
a group of ray florets, occurring in such plants as the daisy
8.
  1. any radial or radiating part, such as a spoke
  2. (as modifier): a radius arm
9.
the lateral displacement of a cam or eccentric wheel
10.
a circular area of a size indicated by the length of its radius: the police stopped every lorry within a radius of four miles
11.
the operational limit of a ship, aircraft, etc
Word Origin
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
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Word Origin and History for radii

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
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radii in Medicine

radius ra·di·us (rā'dē-əs)
n. pl. ra·di·us·es or ra·di·i (-dē-ī')

  1. A line segment that joins the center of a circle with any point on its circumference.

  2. 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.
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radii in Science
radius
  (rā'dē-əs)   
Plural radii (rā'dē-ī') or radiuses
  1. 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.

  2. 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 © 2002. Published by Houghton Mifflin. All rights reserved.
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Encyclopedia Article for radii

radius

in anatomy, the outer of the two bones of the forearm when viewed with the palm facing forward. All land vertebrates have this bone. In humans it is shorter than the other bone of the forearm, the ulna.

Learn more about radius with a free trial on Britannica.com
Encyclopedia Britannica, 2008. Encyclopedia Britannica Online.
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