radius
pronunciation
How to pronounce radius in British English:
UK [ˈreɪdiəs]
How to pronounce radius in American English:
US [ˈreɪdiəs]
-
- Noun:
- the length of a line segment between the center and circumference of a circle or sphere
- a straight line from the center to the perimeter of a circle (or from the center to the surface of a sphere)
- a circular region whose area is indicated by the length of its radius
- the outer and slightly shorter of the two bones of the human forearm
- support consisting of a radial member of a wheel joining the hub to the rim
Word Origin
- radius (n.)
- 1590s, "cross-shaft," from Latin radius "staff, stake, rod; spoke of a wheel; ray of light, beam of light; radius of a circle," of unknown origin. Perhaps related to radix "root," but Tucker suggests connection to Sanskrit vardhate "rises, makes grow," via root *neredh- "rise, out, extend forth;" or else Greek ardis "sharp point." The geometric sense first recorded 1610s. Plural is radii. Meaning "circular area of defined distance around some place" is attested from 1953. Meaning "shorter bone of the forearm" is from 1610s in English (the Latin word had been used thus by the Romans).
Example
- 1. Tens of thousands of people live within the radius .
- 2. Thousands of residents within a 20-kilometer radius of the reactor have been evacuated as a precaution .
- 3. Specifically , luminosity is proportional to radius squared .
- 4. Saturday morning they increased the evacuation radius to 10 kilometers .
- 5. Nuclear blast and wind destroyed buildings within its 1.5-mile radius .