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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: a penumbra of secrecy.
U.S. Law. a right or set of rights implicit but not expressed in the U.S. Constitution or Bill of Rights: The principle of the penumbra protects against an imperfect, or incomplete, enumeration of rights.
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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, penumbral, penurious, penury, Penutian, Penza
Dictionary.com Unabridged
Based on the Random House Unabridged Dictionary, © Random House, Inc. 2023
How to use penumbra in a sentence
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
Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
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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