noun
radius
RAY-dee-uhs
noun
1
A straight line from the center of a circle or sphere to its edge, or the length of that line.
"The radius of the circle is exactly five centimeters."
2
A surrounding area or distance measured from a central point.
"Every school within a five-mile radius was closed for the storm."
3
The long bone of the forearm on the thumb side.
"He fractured his radius after falling off his bike."
How to Use Radius
Learner’s notesIn plain EnglishThe distance from the center of a circle to its edge, or (loosely) the surrounding area within a given distance; also a bone in the forearm.
Common pairings
within a mile radius
radius of the circle
fractured radius
Word Forms
radiused past tense, radii plural, radiuses plural, radiuses singular
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The _____ of the circle is exactly five centimeters.
Etymology
Borrowed directly from Latin radius, meaning "ray" or "spoke".