# radian

> English word · Noun · IPA /ˈɹeɪdiən/ · frequency rank #82,702

## Definitions
1. In the International System of Units, the derived unit of plane angle: the angle subtended at the centre of a circle by an arc of its circumference equal in length to the radius of the circle.

## Etymology
From radius + -an.

## Source
Compiled from Wiktionary via kaikki.org (CC BY-SA). Data vintage: 2026-05-06.
Canonical page: https://plainspell.com/en/word/radian