penumbra

[ pi-nuhm-bruh ]

/ pɪˈnʌm brə /

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.

Words nearby penumbra

pentylenetetrazol, penuche, penuchle, penult, penultimate, penumbra, penurious, penury, penutian, penza, penzance

Origin of penumbra

1660–70; < New Latin, equivalent to Latin paen- pen- + umbra shade

OTHER WORDS FROM penumbra

pe·num·bral, pe·num·brous, adjective

Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

Examples from the Web for penumbra

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|DAILY BEAST
I want to whisper low-toned, intimate talk, in keeping with this penumbra of the dusk.
Glimpses of Bengal|Sir Rabindranath Tagore
This is the entrance into the “penumbra” (or “Partial shade”).
The Story of Eclipses|George Chambers
They are generally surrounded by an aureola known as the penumbra, and sensibly less luminous than the other portions of the orb.
Chambers's Edinburgh Journal, No. 441|Various

Each spot is quite sharply divided into an umbra and a penumbra.
Astronomy for Young Folks|Isabel Martin Lewis
Now I will try and explain to you what the Penumbra is and how it is produced.
The Life of Roger Langdon|Roger Langdon

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, adjective

Word 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.