plural of radian

(geometry) In the International System of Units, the derived unit of plane angular measure of angle equal to the angle subtended at the centre of a circle by an arc of its circumference equal in length to the radius of the circle. Symbol: rad

A spherical region of radius λ/2π around a small dipole electromagnetic antenna. This is the distance at which the induction and radiation terms are equal in magnitude. Inside, the induction terms dominate. In radio antenna theory the radiansphere is a convenient definition for the boundary between near-field and far-field regions.

plural of radiansphere