Definition

A unit used to measure angles, defined as the angle formed at the center of a circle by an arc that is the same length as the radius of that circle.

Example

In mathematics, angles are often measured in radians instead of degrees.

Conversation

Have you ever heard of a radian?

Yeah, I learned about it in math class. It's pretty interesting!

Right? A radian is actually the angle made by an arc equal to the radius.

Exactly! I think it's useful for understanding circles better.

Synonyms & Antonyms

Root Explanation

Radian → It is formed from 'radius' (from Latin 'radius', meaning ray or spoke) and the suffix '-an' (indicating a relation to). A radian is a unit of angular measure that relates to the radius of a circle.

Memory Tip

Think of 'radius' as the line from the center of a circle to its edge, and remember that a radian is a way to measure angles based on that radius.

Visually Confused Words