radius

C2+ Topic:General Vocabulary

US /ˈreɪdiəs/ UK /ˈreɪdiəs/ See IPA manual

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

Simplified etymology

Radius entered English in the late 16th century from Latin radius, meaning “spoke” or “ray.” The same Latin word is the source of ray, radiate, and radio.

Etymology

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

radius Latin

View etymology graph ->

Topics

General Vocabulary

External links

# 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
- General Vocabulary

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