penumbra

[ pi-nuhm-bruh ]

noun

, plural pe·num·brae [pi-, nuhm, -bree], pe·num·bras.

1. Astronomy.
   1. 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 ).
   2. the grayish marginal portion of a sunspot. Compare umbra ( def 3b ).
2. a shadowy, indefinite, or marginal area:

   a penumbra of secrecy.

3. 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.

penumbra

/ pɪˈnʌmbrə /

noun

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

penumbra

/ pĭ-nŭm′brə /

, Plural penumbras 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.
2. See Note at eclipse
3. The grayish outer part of a sunspot.
4. Compare umbra

Derived Forms

• peˈnumbral, adjective

Other Words From

• pe·num·bral pe·num·brous adjective

Word History and Origins

Origin of penumbra¹

First recorded in 1660–65; from New Latin penumbra (coined by Johannes Kepler in 1604), equivalent to Latin paen- prefix meaning “almost” + umbra “shade”; pen-, umbra

Word History and Origins

Origin of penumbra¹

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

Example Sentences

Yes, both injuries are experienced during a traumatic event; however, the psychological penumbra is very different.

From 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.

From The Daily Beast

It formed, as it were, a penumbra of fine shrilling, and could be heard for many streets in advance.

From Project Gutenberg

The penumbra will last quite a long time yet, but it will gradually get fainter and fainter.

From Project Gutenberg

And the concert ended, and soon they were alone together in the flower-filled, fragrant penumbra of the moving carriage.

From Project Gutenberg

He has touched even the dark penumbra of treason; that could not but risk the sum of his other strivings.

From Project Gutenberg

This portion was the kernel of the inheritance, surrounded by a wide penumbra of more feeble light and fewer privileges.

From Project Gutenberg

Related Words

• dark
• gloom
• obscurity
• shade