umbra

Concise Oxford English Dictionary © 2008 Oxford University Press:
umbra /ˈʌmbrə/

▶noun (pl. umbras or umbrae /-briː/)

• 1 the fully shaded inner region of a shadow cast by an opaque object, especially the area on the earth or moon experiencing totality in an eclipse.

• 2 Astronomy the dark central part of a sunspot.

– derivatives
umbral adjective.

– origin C16 (denoting a ghost): from L., lit. ‘shade’.