penumbra
Say it: pih-NUM-bruh /pɪˈnʌmbrə/ · noun
What “penumbra” means
The partly shaded edge around a darker shadow.
More precisely: The partly shaded outer edge of a shadow; a fringe area of uncertainty.
When to use it
For a shadow's softer edge, or formally for an area where rules or answers are unclear.
Memory trick
Latin paene means almost and umbra means shadow: an almost complete shadow.
It can also mean
It can also mean an area where the facts or rules are unclear.
Similar words
half-shadow, fringe, grey area
Where it comes from
Latin paene 'almost' and umbra 'shadow'.
Quick check
A lamp casts a dark shadow with a softer, partly shaded border. What is that outer border called?
the penumbra or the umbra?
Show the answer
the penumbra
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