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Webster 1913 Edition

Penumbra

Pe-num′bra

,
Noun.
[NL., fr. L.
paene
almost +
umbra
shade.]
1.
An incomplete or partial shadow.
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.
☞ The faint shade surrounding the dark central portion of a solar spot is also called the
penumbra
, and sometimes
umbra
.
3.
(Paint.)
The part of a picture where the shade imperceptibly blends with the light.

Webster 1828 Edition

Penumbra

PENUM'BRA

,
Noun.
[L.pene, almost,and umbra,shade.] In astronomy, a partial shade or obscurity on the margin of the perfect shade in an eclipse, or between the perfect shade, where the light is entirely intercepted,and the full light.

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