radius

noun

ra·​di·​us ˈrā-dē-əs 

plural radii ˈrā-dē-ˌī  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

The booking is quite a coup — SZA is the premier headliner at Lollapalooza in Chicago in August, where radius clauses in the past have sometimes prevented the same bookings at Summerfest. —Journal Sentinel, 5 Apr. 2024

The diner chain got that crazy large number by using the measurements of standard Denny’s pancake – six inches in diameter and three inches in radius, for a surface area of 28.27 square inches. —The Indianapolis Star, 5 Apr. 2024

That's because, despite modern technology, the sun's radius is difficult to measure. —The Enquirer, 2 Apr. 2024

Deliberate strikes might have been analyzed by multiple working groups, and precautions taken to limit civilian casualties by using a more precise weapon with a smaller blast radius. —Phil Klay, The Atlantic, 28 Mar. 2024

The sportsbooks at Capital One Arena and Nationals Park offer mobile platforms that are restricted to a two-block radius of the facility. —Michael Brice-Saddler, Washington Post, 20 Mar. 2024

The resort fee covers a range of properly appealing inclusions, such as transportation within a 3-mile radius, a daily yoga class, and rentals of e-bikes, surfboards, and wetsuits. —Alesandra Dubin, Travel + Leisure, 19 Mar. 2024

Within a 30-mile radius, there are roughly 3,200 factories, warehouses and distribution centers that potentially use the port, according to Vakil. —David J. Lynch, Washington Post, 26 Mar. 2024

In Maricopa County, there is also an outdoor siren system within a 10-mile radius of the Palo Verde Generating Station in Wintersburg to warn those in the vicinity of any emergencies associated with the nuclear power plant. —Madeline Nguyen, The Arizona Republic, 22 Mar. 2024

Word History

Etymology

Latin, ray, radius

First Known Use

1578, in the meaning defined at sense 1

Phrases Containing radius

• radius of curvature
• radius vector

Kids Definition

radius

noun

ra·​di·​us ˈrād-ē-əs 

plural radii -ē-ˌī  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

: 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