## steradian

[stə rā**′**dē ən]

noun

the basic unit of solid angular measure in the SI system, equal to the solid angle subtended at the center of a sphere by an area, on its surface, that is equal to the square of its radius: one sphere equals 4π steradians: abbrev.

*sr*Origin of steradian

ste(reo)- + radian## steradian

noun

*Abbr.*

**sr**

A unit of measure equal to the solid angle subtended at the center of a sphere by an area on the surface of the sphere that is equal to the radius squared. The total solid angle of a sphere is 4&pgr; steradians.

Origin of steradian

**ste(reo)–**+

**radian**.

**steradian**

If A = r2 then solid angle &OHgr; = 1 sr.

## steradian

Noun

(*plural* steradians)

- (geometry) In the International System of Units, the derived unit of solid angle; the solid angle subtended at the centre of a sphere of radius
*r*by a portion of the surface of the sphere that has area*r*^{2}. Symbol: sr

Origin

ste(reo) + radian