umbra

American  

[uhm-bruh] / ˈʌm brə /

noun

plural

umbras, umbrae

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 /

plural

umbras

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

• umbral adjective

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

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

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

When the moon passes partially into the umbra, it creates a partial eclipse, which looks as if there’s been a bite taken out of the moon.

From Slate • Apr. 5, 2024

A solar eclipse occurs when a new moon aligns perfectly between Earth and the sun and briefly casts a shadow on our planet, called an umbra.

From National Geographic • Oct. 2, 2023

All were in the umbra of the magnificent hemlock.

From "Frightful's Mountain" by Jean Craighead George

Related Words

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