plural radii
ˈrā-dē-ˌī 
also radiuses
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
Webb recalled that the Denver Fire Department refused to allow the converted Flour Mill Lofts to open because the traffic circle in front was too tight for the turning radius of a fire truck.
—
Aldo Svaldi, The Denver Post, 24 Jan. 2025
By the time the sun rose over the ruins, 17 people were dead within a roughly two-mile radius.
—Claire Fahy, New York Times, 22 Jan. 2025
Supercharged Slam no longer has uncapped radius for aftershocks, capped to 3 meters.
—Paul Tassi, Forbes, 16 Jan. 2025
Everyone within her radius bears the germophobe’s wrath, with the only one who can occasionally pierce through her bilious anger being her upbeat hair-stylist sister Chantal (Michelle Austin), a mother of two vibrant daughters.
—Randy Myers, The Mercury News, 10 Jan. 2025
See all Example Sentences for radius 
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Aldo Svaldi, The Denver Post, 24 Jan. 2025
By the time the sun rose over the ruins, 17 people were dead within a roughly two-mile radius.
—Claire Fahy, New York Times, 22 Jan. 2025
Supercharged Slam no longer has uncapped radius for aftershocks, capped to 3 meters.
—Paul Tassi, Forbes, 16 Jan. 2025
Everyone within her radius bears the germophobe’s wrath, with the only one who can occasionally pierce through her bilious anger being her upbeat hair-stylist sister Chantal (Michelle Austin), a mother of two vibrant daughters.
—Randy Myers, The Mercury News, 10 Jan. 2025
See all Example Sentences for radius
Dictionary Entries Near radius
Cite this Entry
“Radius.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/radius. Accessed 31 Jan. 2025.
Copy CitationKids Definition
radius
noun
ra·di·us
ˈrād-ē-əs
plural radii
-ē-ˌī
also radiuses
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
plural radii
-ē-ˌī
also radiuses
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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