Penumbra
/pɪˈnʌm.brə/noun
The partially shaded outer region of a shadow, especially during an eclipse.
Did you know?The word was coined in Latin scientific writing to describe the fuzzy border of an eclipse shadow, and it comes from *paene* (“almost”) + *umbra* (“shadow”), making it a precise, hauntingly literal term.
Etymological Timeline
Latin
Latin
paene umbra
“almost shadow”
17th Century
New Latin
penumbra
“the partial shadow around the full shadow in an eclipse”
17th Century
English
penumbra
“the lighter outer part of a shadow”
Modern English
English
penumbra
“the partially shaded outer region of a shadow, especially during an eclipse”