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
There must be no further lightning strikes detected within an eight-mile radius for a full 30 minutes before play is permitted to resume.
—
Amelie Claydon,
New York Times,
29 June 2026
Additionally, the hotel offers shuttle services to attractions within a six-mile radius, including Seven Mile Beach.
—
Chadner Navarro,
Travel + Leisure,
29 June 2026
Law enforcement was able to track down the robber using a geofence warrant that included the location data for every cellphone within a 150-meter radius of the robbery.
—
Devin Dwyer,
ABC News,
29 June 2026
Prayers, indeed, are needed in these cases – where the blast radius extends far beyond the accused.
—
Denise Crosby,
Chicago Tribune,
28 June 2026
See All Example Sentences for radius
Examples are automatically compiled from online sources to
show current usage.
Read More
Opinions expressed in the examples do not represent those of Merriam-Webster or its editors.
Send us feedback.
Amelie Claydon,
New York Times,
29 June 2026
Additionally, the hotel offers shuttle services to attractions within a six-mile radius, including Seven Mile Beach.
—
Chadner Navarro,
Travel + Leisure,
29 June 2026
Law enforcement was able to track down the robber using a geofence warrant that included the location data for every cellphone within a 150-meter radius of the robbery.
—
Devin Dwyer,
ABC News,
29 June 2026
Prayers, indeed, are needed in these cases – where the blast radius extends far beyond the accused.
—
Denise Crosby,
Chicago Tribune,
28 June 2026
See All Example Sentences for radius
Cite this Entry
“Radius.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/radius. Accessed 3 Jul. 2026.
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
Love words? Need even more definitions?
Merriam-Webster unabridged
