radius

noun

ra·​di·​us ˈrā-dē-əs How to pronounce radius (audio)
plural radii ˈrā-dē-ˌī How to pronounce radius (audio) also radiuses
1
: a line segment extending from the center of a circle or sphere to the circumference or bounding surface
2
a
: the bone on the thumb side of the human forearm
also : a corresponding part of vertebrates above fishes
b
: the third and usually largest vein of an insect's wing
3
a
: the length of a radius
a truck with a short turning radius
b
: the circular area defined by a stated radius
c
: a bounded or circumscribed area
4
: a radial part
5
: the distance from a center line or point to an axis of rotation

Examples of radius in a Sentence

Measure the radius of the circle. a radius of 10 inches The new museum is expected to draw people from a wide radius. There are three restaurants within a one-block radius of our apartment.
Recent Examples on the Web It is based on a decentralized urban planning model in which all residents' needs are met within a 15-minute radius, regardless of the mode of transport used (on foot, by bike, by public transport). Arnaud Devigne, Forbes, 21 Feb. 2024 Its 17 kilometer radius is regarded as the longest in the world for a commercial delivery drone. Byryan Hogg, Fortune Europe, 20 Feb. 2024 There were also three child-on-child gun homicides over the same time period within a mile radius in Canton, Miss., according to the nonprofit. Robert Gebeloff, New York Times, 16 Feb. 2024 For example, the Vector Control District says citronella candles are effective at repelling mosquitoes only in the immediate radius around the candle, and only in the absence of a breeze. Karen Garcia, Los Angeles Times, 14 Feb. 2024 Three churches in the area of the neighborhood — First Pilgrim Baptist Church, First Institutional Baptist Church and Historic Tanner Chapel African Methodist Episcopal Church — were all within a one-mile radius of each other in the Eastlake neighborhood. The Arizona Republic, 14 Jan. 2024 Computer models indicate most places within a one county radius of the District should warm above freezing between 9 and 11 a.m. Dan Stillman, Washington Post, 5 Jan. 2024 The cooldown is increasing from seven to nine seconds, the knockback will be reduced by 10% and the explosion radius is being tuned down from eight meters to six. Kris Holt, Forbes, 12 Feb. 2024 On Thursday, Prince George’s County police said Stallings-Brown, 31, went on a 90-minute, random rampage that left six people, including a 15-year-old girl, injured across a 12-mile radius between Lanham and Largo in Maryland. Keith L. Alexander, Washington Post, 28 Jan. 2024 See More

These examples are programmatically compiled from various online sources to illustrate current usage of the word 'radius.' Any opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback about these examples.

Word History

Etymology

Latin, ray, radius

First Known Use

1578, in the meaning defined at sense 1

Time Traveler
The first known use of radius was in 1578

Dictionary Entries Near radius

Cite this Entry

“Radius.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/radius. Accessed 2 Mar. 2024.

Kids Definition

radius

noun
ra·​di·​us ˈrād-ē-əs How to pronounce radius (audio)
plural radii -ē-ˌī How to pronounce radius (audio) also radiuses
1
: the bone on the thumb side of the human forearm
also : a corresponding bone of other vertebrates
2
: a line extending from the center of a circle or sphere to the circumference or surface
3
a
: the length of a radius
b
: a circular area defined by a given radius
deer may wander within a radius of several miles
4
: a radial part or plane
Etymology

from Latin radius "ray, beam, spoke" — related to radiate, radio, ray entry 2

Medical Definition

radius

noun
ra·​di·​us ˈrād-ē-əs How to pronounce radius (audio)
plural radii -ē-ˌī How to pronounce radius (audio) also radiuses
: the bone on the thumb side of the human forearm or on the corresponding part of the forelimb of vertebrates above fishes that in humans is movably articulated with the ulna at both ends so as to permit partial rotation about that bone, that bears on its inner aspect somewhat distal to the head a prominence for the insertion of the biceps tendon, and that has the lower end broadened for articulation with the proximal bones of the carpus so that rotation of the radius involves also that of the hand
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