(pĭ-nŭm'brə) pronunciation
n., pl., -brae (-brē), or -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).

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

penumbral pe·num'bral or pe·num'brous adj.

(1) The lighter, outer shadow of a double-shadow effect produced by a large, unfocused source of light shining on an interfering opaque object. A penumbral eclipse is one in which the eclipsed object passes through the penumbral shadow. (2) The lighter area, marked by radial filaments, that may surround the darker, central umbra of a sunspot. Penumbral waves are waves observed in the light of H-alpha that move out from the center of a sunspot across the penumbra.


    Comparative darkness that results from the blocking of light rays: shade, shadow, umbra, umbrage. See light/darkness.

A blurred edge to an image, a halo effect, in an x-ray film caused usually by an overlarge focal spot exacerbated by a long object-to-film distance.

Random House Word Menu:

categories related to 'penumbra'

Random House Word Menu by Stephen Glazier
For a list of words related to penumbra, see:
  • Optics - penumbra: partially illuminated portion of a shadow
  • Celestial Phenomena and Points - penumbra: partly lighted area that surrounds complete shadow of celestial body during eclipse




Dansk (Danish)
n. - halvskygge

Nederlands (Dutch)
halfschaduw, donker gebied rondom zonnevlek, periferie, vaag/ onduidelijk gebied, rechten impliciet in grondwet

Français (French)
n. - (Astron) pénombre (littér)

Deutsch (German)
n. - Halbschatten

Ελληνική (Greek)
n. - σκιόφως

Italiano (Italian)

Português (Portuguese)
n. - penumbra (f)

Русский (Russian)

Español (Spanish)
n. - penumbra

Svenska (Swedish)
n. - halvskugga

中文(简体)(Chinese (Simplified))

中文(繁體)(Chinese (Traditional))
n. - 半影

한국어 (Korean)
n. - 반영, 명암 농담의 경계 부분, 어두운 그림자

日本語 (Japanese)
n. - 半影, 明暗の境目

العربيه (Arabic)
‏(الاسم) شبه ظل, ظليل‏

עברית (Hebrew)
n. - ‮צל אפור וחיוור העוטר לפעמים את הצל השחור המלא, פלג-צל‬

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