steradianach

Steradianach is a term that has appeared in some niche discussions as a variation or generalization of the steradian, the SI unit of solid angle. It is not an officially recognized unit, and it does not appear in the International System of Units. In formal use, the term is sometimes described as a weighted solid-angle measure designed to capture anisotropic directional patterns.

Definition: Steradianach is defined as the integral over a region of a dimensionless weighting function w(Ω) times the differential solid angle dΩ: Steradianach = ∫Region w(Ω) dΩ. The unit remains that of solid angle because dΩ carries the unit sr, and w is dimensionless. When the weighting is uniform (w(Ω) = 1 everywhere within the region), the steradianach equals the ordinary solid angle of that region. For the full sphere, this yields 4π steradians.

Notational conventions vary; there is no official symbol or abbreviation. In literature that mentions steradianach, it is sometimes denoted informally as sra or sr_a, but such usage is nonstandard.

Applications, where invoked, focus on contexts with anisotropic emission or reception, such as radiation patterns, lighting calculations, or directional sensing. The steradianach concept allows a single scalar measure to reflect both angular extent and directional weighting, contrasting with the plain solid angle which treats all directions equally.

Status: The term remains informal and nonstandard. It is chiefly of interest in theoretical discussions or educational illustrations about how weighting changes perceived angular coverage. See also steradian; solid angle; anisotropy.