umbra

noun8

1. •
   The fully shaded inner region of a shadow cast by an opaque object.
2. •
   The area on the earth or moon experiencing the total phase of an eclipse.
3. •
   (literary) A shadow.
4. •
   The central region of a sunspot.
5. •
   An element of the umbral calculus.

   • In order to set up such an algorithm, we need the notion of multiplicative inverse of an umbra. Two umbrae are said to be multiplicative inverse to each other when αγ ≡ u. — 2009
6. •
   One of the family Umbridae of mudminnows.
7. •
   One of genus Umbrina of drums (family Sciaenidae).
8. •
   (no longer used) An uninvited guest brought along by one who was invited.