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umbra

[uhm-bruh]
See more synonyms for umbra on Thesaurus.com
noun, plural um·bras, um·brae [uhm-bree] /ˈʌm bri/.
  1. shade; shadow.
  2. the invariable or characteristic accompaniment or companion of a person or thing.
  3. Astronomy.
    1. the complete or perfect shadow of an opaque body, as a planet, where the direct light from the source of illumination is completely cut off.Compare penumbra(def 1a).
    2. the dark central portion of a sunspot.Compare penumbra(def 1b).
  4. a phantom or shadowy apparition, as of someone or something not physically present; ghost; spectral image.
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Origin of umbra

1590–1600; < Latin: shade, shadow
Related formsum·bral, adjective
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

Examples from the Web for umbra

Historical Examples

  • Durois advised me that the Kyng of Umbra had put two padres to death, viz.

    Diary of Richard Cocks Vol. I

    Richard Cocks

  • Diagram of the use of the Umbra Versa, at two observations; Astrol.

  • Each spot is quite sharply divided into an umbra and a penumbra.

    Astronomy for Young Folks

    Isabel Martin Lewis

  • Sedentes in tenebris, et in umbra mortis, vinctos in mendicitate.

    The Dance of Death

    Francis Douce

  • He was Maulevrier's Umbra, and must go where his patron went.

British Dictionary definitions for umbra

umbra

noun plural -brae (-briː) or -bras
  1. a region of complete shadow resulting from the total obstruction of light by an opaque object, esp the shadow cast by the moon onto the earth during a solar eclipse
  2. the darker inner region of a sunspot
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Compare penumbra
Derived Formsumbral, adjective

Word Origin

C16: from Latin: shade, shadow
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Word Origin and History for umbra

n.

1590s, "phantom, ghost," a figurative use from Latin umbra "shade, shadow" (see umbrage). Astronomical sense of "shadow cast by the earth or moon during an eclipse" is first recorded 1670s. Meaning "an uninvited guest accompanying an invited one" is from 1690s.

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Online Etymology Dictionary, © 2010 Douglas Harper
umbra in Science

umbra

[ŭm′brə]
Plural umbras umbrae (ŭm′brē)
  1. The darkest part of a shadow, especially the cone-shaped region of full shadow cast by Earth, the Moon, or another body during an eclipse. In a full lunar eclipse, which generally lasts for one or two hours, the entire disk of the Moon is darkened as it passes through the umbra. During this period the Moon takes on a faint reddish glow due to illumination by a small amount of sunlight that is refracted through the Earth's atmosphere and bent toward the darkened Moon; the reddish tint is caused by the filtering out of blue wavelengths as the sunlight passes through the Earth's atmosphere, leaving only the longer wavelengths on the red end of the spectrum. See Note at eclipse.
  2. The dark central region of a sunspot. Compare penumbra.
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The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.