radius

C2+ Topic:Space, Position & Direction

US /ˈreɪdiəs/ UK /ˈreɪdiəs/ See IPA manual

noun

Meanings

1

noun
a straight line from the center to the circumference of a circle

The sprinklers cover everything within a ten-meter radius.

Thesaurus

Synonyms

1 noun · a straight line from the... spoke ray range reach extent

Word family

Derived forms radialradian

Related forms radiate radiation radioradii

Etymology

From Latin radius ('staff, rod, spoke of a wheel, ray of light'), of uncertain ultimate origin.

radius Latin

View etymology graph ->

Topics

Space, Position & Direction

# radius

**Type:** Word
**Level:** C2+
**Part of speech:** noun
**IPA (US):** ˈreɪdiəs
**IPA (UK):** ˈreɪdiəs

## Meanings
1. a straight line from the center to the circumference of a circle

## Examples
- The sprinklers cover everything within a ten-meter radius.

## Synonyms
- spoke
- ray
- range
- reach
- extent

## Derived Forms
- radial
- radian

## Related Forms
- radiate
- radiation
- radio
- radii

## Roots and Affixes
- Root: radius

## Etymology
From Latin radius ('staff, rod, spoke of a wheel, ray of light'), of uncertain ultimate origin.

## AI Etymology
Radius comes from Latin radius ('staff, rod, spoke of a wheel, ray of light'), of uncertain ultimate origin. The form is best read as a historical transfer or inheritance, with its older language material carrying the main semantic load. As a noun, it denotes "a straight line from the center to the circumference of a circle", keeping the historical idea close to its dictionary sense. Relevant historical forms include Latin radius. Derivative forms include radial, radian; related words include radiate, radiation, radio, radii.

## Topics
- Space, Position & Direction

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radius

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