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
In response to the detections, more than 100 other all commercial poultry operations within a 6-mile radius were placed under quarantine and went through surveillance testing.
—
Rebekah Riess, CNN, 11 Feb. 2025
Option for older adults to skip driving Anaheim also offers a Senior Wheels Program for active older adults aged 60 and over residing in Anaheim and Anaheim Hills which can be utilized within a 10-mile radius of their home.
—Sharon Hlapcich, Orange County Register, 6 Feb. 2025
The reserve is located within a two-mile radius of the plant.
—James Powel, USA TODAY, 29 Jan. 2025
Under the agreement, people within a 10-mile radius of the crash could opt into a separate personal injury payment of up to $25,000 for any medical issues resulting from the derailment.
—Shradha Dinesh, NPR, 3 Feb. 2025
See all Example Sentences for radius 
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Rebekah Riess, CNN, 11 Feb. 2025
Option for older adults to skip driving Anaheim also offers a Senior Wheels Program for active older adults aged 60 and over residing in Anaheim and Anaheim Hills which can be utilized within a 10-mile radius of their home.
—Sharon Hlapcich, Orange County Register, 6 Feb. 2025
The reserve is located within a two-mile radius of the plant.
—James Powel, USA TODAY, 29 Jan. 2025
Under the agreement, people within a 10-mile radius of the crash could opt into a separate personal injury payment of up to $25,000 for any medical issues resulting from the derailment.
—Shradha Dinesh, NPR, 3 Feb. 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 21 Feb. 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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