radius

noun
ra·​di·​us | \ ˈrā-dē-əs How to pronounce radius (audio) \
plural radii\ ˈrā-​dē-​ˌī How to pronounce radii (audio) \ also radiuses

Definition of radius

1 : a line segment extending from the center of a circle or sphere to the circumference or bounding surface
2a : 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
3a : 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.
See More

Recent Examples on the Web

But radar shows no rain within a one country radius of the District. Greg Porter, Washington Post, "PM Update: Muggy but dry for tonight’s fireworks as most storms should stay well west," 4 July 2018 According to a new report from Breathe Free Detroit, which cited EPA statistics, almost 22,000 people live within a 1½-mile radius of the incinerator. Katrease Stafford, Detroit Free Press, "Detroit Renewable Power waste incinerator pollutes. Is DEQ doing enough?," 21 May 2018 Trine has a studio in Long Beach, California, and manufactures all of his furniture within a 30-mile radius. Madeleine Luckel, Vogue, "16 of the Most Innovative Furniture Designers Who Manufacture in the U.S.," 4 July 2018 The goal: For the 30 days of June, eat only foods that were grown, caught or raised within a 200-mile radius of New Orleans. Molly Kimball, NOLA.com, "2018 Eat Local Challenge: No need to go hardcore to dig in," 22 May 2018 In fact, Fabletics enjoys a two-and-a-half times increase in revenue from its most active customers within a 30-mile radius of a Fabletics store. Anne D'innocenzio, The Seattle Times, "Brands born on the internet embrace physical stores," 12 Dec. 2018 Both those locations are within a 5-block radius of Amazon’s HQ2. Natt Garun, The Verge, "For Queens residents, Amazon’s HQ2 isn’t arriving without a fight," 20 Nov. 2018 Almost all ingredients are sourced within a 20-mile radius. Tyler Wetherall, Condé Nast Traveler, "Kent Is Poised to Be the U.K.'s Napa Valley," 14 Sep. 2018 Basically, there was enough glitter to ensure that anyone within a 10-foot radius of that box would be wiping away the errant sparkle for days afterward. Candace Braun Davison, House Beautiful, "Can Marie Kondo Conquer Caboodles?," 17 Aug. 2018

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'radius.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

See More

First Known Use of radius

1578, in the meaning defined at sense 1

History and Etymology for radius

Latin, ray, radius

Keep scrolling for more

Learn More about radius

Statistics for radius

Last Updated

9 Mar 2019

Look-up Popularity

Time Traveler for radius

The first known use of radius was in 1578

See more words from the same year

Keep scrolling for more

More Definitions for radius

radius

noun

English Language Learners Definition of radius

technical : a straight line from the center of a circle or sphere to any point on the outer edge also : the length of this line
: an area that goes outward in all directions from a particular place
medical : the bone in the lower part of your arm on the same side as your thumb

radius

noun
ra·​di·​us | \ ˈrā-dē-əs How to pronounce radius (audio) \
plural radii\ -​dē-​ˌī \

Kids Definition of radius

1 : a straight line extending from the center of a circle to the outside edge or from the center of a sphere to the surface
2 : an area that extends in all directions from a place Most students live within a radius of five miles from the school.
3 : the bone on the thumb side of the arm between the wrist and the elbow

radius

noun
ra·​di·​us | \ ˈrād-ē-əs How to pronounce radius (audio) \
plural radii\ -​ē-​ˌī How to pronounce radii (audio) \ also radiuses

Medical Definition of radius

: 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

Keep scrolling for more

More from Merriam-Webster on radius

Spanish Central: Translation of radius

Nglish: Translation of radius for Spanish Speakers

Britannica English: Translation of radius for Arabic Speakers

Britannica.com: Encyclopedia article about radius

Comments on radius

What made you want to look up radius? Please tell us where you read or heard it (including the quote, if possible).

WORD OF THE DAY

the range of authority or knowledge

Get Word of the Day daily email!

Test Your Vocabulary

Original Meanings Quiz

  • rembrandt-painting-a-young-scholar-and-his-tutor
  • Which of the following is the earliest known sense of the word awe?
True or False

Test your knowledge - and maybe learn something along the way.

TAKE THE QUIZ
Word Winder's CrossWinder

Test Your Knowledge - and learn some interesting things along the way.

TAKE THE QUIZ

Love words? Need even more definitions?

Subscribe to America's largest dictionary and get thousands more definitions and advanced search—ad free!