#opacity  the phenomenon of not permitting the passage of electromagnetic radiation
  exclusion:  #transparence
  supertype:  #physical_phenomenon  a natural phenomenon involving the physics of matter and energy
  subtype:  #optical_opacity__opticalopacity  opacity to light
  subtype:  #radiopacity__radio-opacity__radioopacity  opacity to X-rays or other radiation

No statement uses or specializes #opacity; click here to add one.