Radius
/ˈreɪdiəs/Definition, CEFR level B2, pronunciation, examples, and quiz.
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Definition
nounA straight line from the center of a circle to its edge.
nounThe area or distance within a particular range.
Extra definitions
nounDistance from center to boundary.
nounA circular area from a center.
nounThe long bone in the forearm, on the side of the thumb.
Sentence Examples
The circle has a radius of five centimeters.
Trees were planted within a radius.
Draw a radius to the edge.
Synonyms & Antonyms
Synonyms:
None
Antonyms:
None
Word Origin & History
Borrowed from Latin radius (“ray”). Doublet of ray.
Literary Quotations & Historical Citations
“It is also obvious, and proved by experiment, that the rotatory motions observed in the hand proceed from the rotatory motions of the radius.”
— 1808, John Barclay, The Muscular Motions of the Human Body, →OCLC, page 396:
“We start with spherical geometries. The two geometries on spheres of radiuses R₁ and R₂ are obviously identical if R₁ = R₂; moreover, the converse also holds.”
— 1994, Viacheslav V. Nikulin, Igor R. Shafarevich, translated by Miles Reid, Geometries and Groups, Springer, page 194:
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CEFR Practice Quiz
The circle has a ____ of five centimeters.