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penumbra
From The Collaborative International Dictionary of English v.0.48:
Penumbra \Pe*num"bra\, n. [NL., fr. L. paene almost + umbra
shade.]
1. An incomplete or partial shadow.
[1913 Webster]
2. (Astron.) The shadow cast, in an eclipse, where the light
is partly, but not wholly, cut off by the intervening
body; the space of partial illumination between the umbra,
or perfect shadow, on all sides, and the full light. --Sir
I. Newton.
[1913 Webster]
Note: The faint shade surrounding the dark central portion of
a solar spot is also called the penumbra, and
sometimes umbra.
[1913 Webster]
3. (Paint.) The part of a picture where the shade
imperceptibly blends with the light.
[1913 Webster]
