penumbra

[ pi-nuhm-bruh ]

See synonyms for penumbra on Thesaurus.com

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.

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”; see pen-, umbra

Other words from penumbra

pe·num·bral, pe·num·brous, adjective

Words Nearby penumbra

Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2023

How to use penumbra in a sentence

Yes, both injuries are experienced during a traumatic event; however, the psychological penumbra is very different.
Study Says Half of Jailed NYC Teens Have History of Brain Injury | Dr. Anand Veeravagu, MD, Tej Azad | April 22, 2014 | THE DAILY BEAST
In person, Waltz is equally charming, but without the penumbra of menace that comes with having Nazi goons just outside the door.
Tarantino's Glorious Nazi | Paul Cullum | August 16, 2009 | THE DAILY BEAST
It formed, as it were, a penumbra of fine shrilling, and could be heard for many streets in advance.
The Dragon Painter | Mary McNeil Fenollosa
The penumbra will last quite a long time yet, but it will gradually get fainter and fainter.
Pharaoh's Broker | Ellsworth Douglass
And the concert ended, and soon they were alone together in the flower-filled, fragrant penumbra of the moving carriage.
The Devourers | Annie Vivanti Chartres

He has touched even the dark penumbra of treason; that could not but risk the sum of his other strivings.
The Posthumous Works of Thomas De Quincey, Vol. 1 (2 vols) | Thomas De Quincey
This portion was the kernel of the inheritance, surrounded by a wide penumbra of more feeble light and fewer privileges.
The Expositor's Bible: The Book of Joshua | William Garden Blaikie

British Dictionary definitions for penumbra

penumbra

/ (pɪˈnʌmbrə) /

nounplural -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

Origin of penumbra

C17: via New Latin from Latin paene almost + umbra shadow

Compare umbra

Derived forms of penumbra

penumbral or penumbrous, adjective

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.

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