penumbra
[ pi-nuhm-bruh ]
/ pɪˈnʌm brə /
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noun, plural pe·num·brae [pi-nuhm-bree], /pɪˈnʌm bri/, pe·num·bras.
Astronomy.
- the partial or imperfect shadow outside the complete shadow of an opaque body, as a planet, where the light from the source of illumination is only partly cut off.Compare umbra (def. 3a).
- the grayish marginal portion of a sunspot.Compare umbra (def. 3b).
a shadowy, indefinite, or marginal area.
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Origin of penumbra
OTHER WORDS FROM penumbra
pe·num·bral, pe·num·brous, adjectiveWords nearby penumbra
pentyl group, penuche, penuchle, penult, penultimate, penumbra, penurious, penury, Penutian, Penza, Penzance
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Based on the Random House Unabridged Dictionary, © Random House, Inc. 2021
Example sentences from the Web for penumbra
British Dictionary definitions for penumbra
penumbra
/ (pɪˈnʌmbrə) /
noun plural -brae (-briː) or -bras
a fringe region of half shadow resulting from the partial obstruction of light by an opaque object
astronomy the lighter and outer region of a sunspot
painting the point or area in which light and shade blend
Compare umbra
Derived forms of penumbra
penumbral or penumbrous, adjectiveWord Origin for penumbra
C17: via New Latin from Latin paene almost + umbra shadow
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition
© William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins
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Scientific definitions for penumbra
penumbra
[ pĭ-nŭm′brə ]
Plural penumbras penumbrae (pĭ-nŭm′brē)
A partial shadow between regions of full shadow (the umbra) and full illumination, especially as cast by Earth, the Moon, or another body during an eclipse. During a partial lunar eclipse, a portion of the Moon's disk remains within the penumbra of Earth's shadow while the rest is darkened by the umbra. See Note at eclipse.
The grayish outer part of a sunspot. Compare umbra.
The American Heritage® Science Dictionary
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