📖 Math Dictionary
Radius
/RAY-dee-us/
Definition
The radius is the distance from the center of a circle to any point on its edge. It is exactly half the diameter. All radii (plural) of a circle are equal in length.
💡Example
If a circle has a diameter of 10 cm, its radius is 10 ÷ 2 = 5 cm. The circumference formula C = 2πr uses the radius. Area formula A = πr² also uses radius.
🎓Used in Grades
Grades 4-10KS2 to GCSEÅrskurs 4-9