umbra

American  

[uhm-bruh] / ˈʌm brə /

noun

• umbras,
  plural
• umbrae
  plural

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.

   2. the dark central portion of a sunspot.

4. a phantom or shadowy apparition, as of someone or something not physically present; ghost; spectral image.

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umbra British  

/ ˈʌmbrə /

noun

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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umbra Scientific  

/ ŭm′brə /

• umbras
  plural

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.

2. See Note at eclipse

3. The dark central region of a sunspot.

4. Compare penumbra

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Other Word Forms

Derived Forms

• umbral
  adjective

Inflected Forms

Nouns

• umbrae
  plural
• umbras
  plural

Etymology

Origin of umbra

First recorded in 1600–10; from Latin: literally, “shade, shadow”

Explanation

The very darkest part of a shadow is the umbra. It's where the light source is completely blocked by the object in front of it. You'll most often encounter the word umbra in astronomy, along with penumbra and sometimes antumbra. During a lunar eclipse, the very darkest, inner part of the Earth's shadow is the umbra, while the lighter shadow at the edge is the penumbra. The antumbra is the bright ring you can sometimes see around the shadow. Umbra is a Latin word that means "shadow."

Example Sentences

See Examples For:

umbra umbrae umbras

At the eclipse's maximum point, about 93% of the Moon's diameter will lie within Earth's dark central shadow, known as the umbra.

From Science Daily ● Aug. 5, 2026

But do not expect there to be a big shadow visible on the supermoon as only around 4% of the Moon's disc will be covered in darkness by the umbra shadow.

From BBC ● Sep. 17, 2024

In this case, about 3.5% of the moon will appear darkened by the Earth’s umbra, a term that describes the darkest segment of the Earth’s shadow.

From Los Angeles Times ● Sep. 17, 2024

And when the moon is fully in the umbra, that’s a total eclipse.

From Slate ● Apr. 5, 2024

All were in the umbra of the magnificent hemlock.

From "Frightful's Mountain" by Jean Craighead George

Plato truly believ'd his archetypal Idēas to possess the fourth dimension: For since our solid is triple, but always Its shade only double, solids as umbrae Must lack equally one dimension also.

From The Poetical Works of Robert Bridges by Robert Bridges

Virgil thought the odour exhaled by the Juniper tree noxious, and he speaks of the Juniperis gravis umbra:—     "Surgamus! solet esse gravis cantantibus umbra;     Juniperis gravis umbra; nocent et frugibus umbrae."

From Herbal Simples Approved for Modern Uses of Cure by William Thomas Fernie

The Justices of that day bore a heavier burden than their successors--hodie nominis umbrae.

From Ovington's Bank by Stanley J. Weyman

Happily these umbrae pallentes have now vanished, and I trust we will make the ties of friendship closer and stronger by establishing between us a community and exchange of prayers.

From Memoirs of James Robert Hope-Scott, Volume 2 by Robert Ornsby

But the ancient /habitues/—the /magni nominis umbrae/, contemporaries of Brummell in his zenith, boon companions of George IV. in his regency— still haunted the spot.

From My Novel — Volume 11 by Edward Bulwer Lytton, Baron Lytton

"Because the umbras have opposite polarities, they attract each other," says the Marshall Center's Moore.

From Time Magazine Archive

Occasionally, the penumbras of two sunspots of opposite polarity merge as they move past each other, putting the oppositely charged umbras in contact.

From Time Magazine Archive

The darker central portions of sunspots, or umbras, have the strongest magnetic fields; the lighter exteriors, or penumbras, the weaker fields.

From Time Magazine Archive

For the 'Segnatura,' which took place on certain days of the week, he selected on each occasion some new shady retreat 'novos in convallibus fontes et novas inveniens umbras, quae dubiam facerent electionem.'

From The Civilisation of the Renaissance in Italy by Jacob Burckhardt

Might we not print above his body the last words of the poem he seems to have loved so much: Fugit indignata sub umbras!

From The Jessica Letters: An Editor's Romance by Paul Elmer More

Related Words

• body
• character
• creature
• ghost
• human being
• individual
• man
• person
• spirit
• woman