penumbra
Americannoun
plural
penumbrae, penumbras-
Astronomy.
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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.
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the grayish marginal portion of a sunspot.
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a shadowy, indefinite, or marginal area.
a penumbra of secrecy.
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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.
noun
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a fringe region of half shadow resulting from the partial obstruction of light by an opaque object
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astronomy the lighter and outer region of a sunspot
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painting the point or area in which light and shade blend
plural
penumbras-
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.
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See Note at eclipse
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The grayish outer part of a sunspot.
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Compare umbra
Other Word Forms
- penumbral adjective
- penumbrous adjective
Etymology
Origin of penumbra
First recorded in 1660–65; from New Latin penumbra (coined by Johannes Kepler in 1604), equivalent to Latin paen- prefix meaning “almost” + umbra “shade”; pen-, umbra
Example Sentences
Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.
A lunar eclipse takes place when the Moon passes through the outer region of Earth's shadow, called the penumbra.
From BBC • Mar. 14, 2025
Supreme Court, fashioned a right to privacy from the penumbra of rights contained in the First, Third, Fourth, Fifth and Ninth Amendments to the U.S.
From Slate • Jan. 18, 2024
His non-adult fiction occupies a penumbra between “not really classics” and “better than most of the crap pushed at kids.”
From Los Angeles Times • Feb. 22, 2023
Dried sunflowers and books fashioned from lead are recurrent themes of a world that hovers in the penumbra between life and death.
From New York Times • Nov. 18, 2022
But such moments were tempered by the long penumbra cast by Everest, which seemed to recede little with the passage of time.
From "Into Thin Air" by Jon Krakauer
Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023
Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.
