Image: Wikimedia Commons

radius

Segment in a circle or sphere from its center to its perimeter or surface and its length

EntityQ173817

Also known as circle radius · radius of a circle

Subclass of: line segment
, radial line
, length
Part of: diameter

Overview

From Wikipedia, the free encyclopedia · Read full article · Text CC BY-SA 4.0

In classical geometry, a radius of a circle or sphere is any of the line segments from its center to its perimeter (circle) or surface (sphere), and, in more modern usage, it is also their length. The radius of a regular polygon is the line segment or distance from its center to any of its vertices. The name comes from the Latin radius, meaning ray but also the spoke of a chariot wheel. The typical abbreviation and mathematical symbol for radius is R or r. By extension, the diameter is defined as twice the radius:

Overview

All data

42 statements · 17% with external sources · numbers in brackets are citations

Main Wikidata property: radius
ISQ dimension: \mathsf{L}
Quantity symbol (LaTeX): r
R
Recommended unit of measurement: metre
2
Sources
1.Stated in ISO 80000-3:2019 Quantities and units — Part 3: Space and time
2.Stated in ISO 80000-3:2006 Quantities and units — Part 3: Space and time
View statement on Wikidata ↗
Different from: Q28022976
radial distance

On other databases

31 identifiers linking radius across the web's reference databases

Data quality

statements

17%

externally sourced

Source last edited August 17, 2026. AIDB refreshes this page daily.

Suggest a fact or correction

Links

Use this data

curl https://aidb.si/api/v1/entities/Q173817

API docs, limits & keys

Cite this page

AIDB. (2026). radius (Q173817). Retrieved from https://aidb.si/e/radius-Q173817