penumbrae

pe·num·bra

[pi-nuhm-bruh]
noun, plural pe·num·brae [-bree] , pe·num·bras.
1.
Astronomy.
a.
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 ).
b.
the grayish marginal portion of a sunspot. Compare umbra ( def 3b ).
2.
a shadowy, indefinite, or marginal area.
Origin:
1660–70; < Neo-Latin, equivalent to Latin paen- pen- + umbra shade

Related forms
pe·num·bral, pe·num·brous, adjective
Dictionary.com Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2013.
Cite This Source Link To penumbrae
Collins
World English Dictionary
penumbra (pɪˈnʌmbrə) [Click for IPA pronunciation guide]
 
—n , pl -brae, -bras
1.  a fringe region of half shadow resulting from the partial obstruction of light by an opaque object
2.  astronomy the lighter and outer region of a sunspot
3.  painting the point or area in which light and shade blend
 
[C17: via New Latin from Latin paene almost + umbra shadow]
 
pe'numbral
 
—adj
 
pe'numbrous
 
—adj

Collins English Dictionary - Complete & Unabridged 10th Edition
2009 © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins
Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009
Cite This Source
00:10
Penumbrae is always a great word to know.
So is lollapalooza. Does it mean:
a scrap or morsel of food left at a meal.
an extraordinary or unusual thing, person, or event; an exceptional example or instance.
LEARN MORE UNUSUAL WORDS WITH WORD DYNAMO...
Etymonline
Word Origin & History

penumbra
1666, from Mod.L. penumbra "partial shadow outside the complete shadow of an eclipse," coined 1604 by Kepler from L. pæne "almost" + umbra "shadow" (see umbrage).
Online Etymology Dictionary, © 2010 Douglas Harper
Cite This Source
American Heritage
Science Dictionary
penumbra   (pĭ-nŭm'brə)  Pronunciation Key 
Plural penumbras or penumbrae (pĭ-nŭm'brē)

  1. 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.

  2. The grayish outer part of a sunspot. Compare umbra.


The American Heritage® Science Dictionary
Copyright © 2002. Published by Houghton Mifflin. All rights reserved.
Cite This Source
Partners:WordBloglinesCitysearchThe Daily BeastAsk AnswersAsk KidsLife123SendoriHome Advisor
Copyright © 2013 Dictionary.com, LLC. All rights reserved.
About PRIVACY POLICY Terms API Careers Advertise with Us Contact Us Suggest a Word Help
  • Please Login or Sign Up to use the Recent Searches feature
FAVORITES
RECENT