Definition of "steradian" []

• 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 4π steradians. See Table at measurement. (noun)

American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

• "(c) In photometry, the unit name steradian and the unit symbol sr are usually retained in expressions for derived units."
• "Unit of luminous intensity candela The candela is the luminous intensity, in a given direction, of a source that emits monochromatic radiation of frequency 540 x 1012 hertz and that has a radiant intensity in that direction of 1/683 watt per steradian."
• "There were some say that this “hole,” which is just a cold spot which has “sharp boundaries” in steradian measure from the surrounding."