EXAMPLES | WORD ORIGIN 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. Origin of penumbra 1660–70;
Latin paen- pen-
Related forms pe·num·bral, pe·num·brous, adjective
Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019
Examples from the Web for penumbral Historical Examples of penumbral British Dictionary definitions for penumbral 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 Derived Forms 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
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Word Origin and History for penumbral n.
1660s, from Modern Latin
penumbra "partial shadow outside the complete shadow of an eclipse," coined 1604 by Kepler from Latin pæne "almost" + umbra "shadow" (see umbrage). Related: Penumbral.
Online Etymology Dictionary, © 2010 Douglas Harper
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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