penumbra

pe·num·bra  (p-nmbr)

n. pl. pe·num·brae (-br) or pe·num·bras

1. A partial shadow, as in an eclipse, between regions of complete shadow and complete illumination. See Synonyms at shade.

2. The grayish outer part of a sunspot.

3. An area in which something exists to a lesser or uncertain degree: "The First Amendment has a penumbra where privacy is protected from governmental intrusion" Joseph A. Califano, Jr.

4. An outlying surrounding region; a periphery: "Downtown Chicago and its penumbra also stand rejuvenated" John McCormick.

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[New Latin pnumbra : Latin paene, almost + Latin umbra, shadow.]

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pe·numbral, pe·numbrous adj.

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penumbra

Noun

pl -brae or -bras

1. the partially shadowed region which surrounds the full shadow in an eclipse

2. Literary a partial shadow [Latin paene almost + umbra shadow]

penumbral adj

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penumbra  (p-nmbr)

Plural penumbras or penumbrae (p-nmbr)

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.

Thesaurus

Noun

1.

penumbra - a fringe region of partial shadow around an umbra shadow - shade within clear boundaries