  Electromagnetic degrees of freedom are instrumental in antenna design,
wireless communications, imaging, and scattering. Larger number of degrees of
freedom enhances control in antenna design, influencing radiation patterns and
directivity, while in communication systems, it links to spatial channels for
increased data rates and reliability, and resolution in imaging. The
correlation between computed degrees of freedom and physical quantities is not
fully understood, prompting a comparison between classical estimates, Weyl's
law, modal expansions, and optimization techniques. In this paper, it is shown
that NDoF for arbitrary shaped radiating structures approaches the shadow area
measured in squared wavelengths.
