#aperture.opening  an opening; usually small
  supertype:  #opening.artifact  a vacant or unobstructed space; "they left a small opening for the cat at the bottom of the door"
  subtype:  #embouchure__mouthpiece  the aperture of a wind instrument into which the player blows directly
  subtype:  #mouthpiece.aperture  a part that goes over or into the mouth of a person; "the mouthpiece of a respirator"

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