Radius Means a Spoke of a Wheel
A radius is the distance from a centre to a circle's edge. The Latin word means a spoke, and it also names a forearm bone.
A radius is the distance from the centre of a circle to its edge. The Latin word means a staff or the spoke of a wheel, which is exactly the geometry. The same word names one of the two forearm bones, and it gives *radiate*, *radiant* and *radio* — all describing something spreading outwards from a centre like spokes.
- Centre to edge distance. *A radius of ten metres.*
- An area around a point. *Within a five-mile radius.*
- A forearm bone. *A fractured radius.*
- Radii — the plural. *Two radii.*
Word forms
| Form | Word | Example |
|---|---|---|
| Noun | radius | The radius of the arc. |
| Plural | radii | Equal radii. |
| Plural | radiuses | Also used. |
| Verb | radiate | Radiate outwards. |
| Related | radio | Radio waves. |
How it is used in a sentence
- The radius is half the diameter.Geometry.
- The radius is the thumb-side forearm bone.Anatomy.
- Radio comes from the same root.Waves radiating outward.
Words from *radius*
- Radiate — to spread out from a centre
- Radiant — shining outward
- Radio — transmission by radiating waves
- Radiation — energy emitted outwards
- Eradicate — unrelated, from *radix*, a root
From Latin *radius*, a staff, spoke or ray of light. Its earlier origin is uncertain.
Radii or radiuses?
Radii is the Latin plural and standard in mathematics. Radiuses appears in general use.
Are radius and radish related?
No. Radish comes from *radix*, a root, which is a different Latin word despite the resemblance.