- shade; shadow.
- the invariable or characteristic accompaniment or companion of a person or thing.
- a phantom or shadowy apparition, as of someone or something not physically present; ghost; spectral image.
Origin of umbra
Examples from the Web for umbral
Outside the umbral cone is that of the penumbra, within which the sun is partially hidden by the moon.
- 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
- the darker inner region of a sunspot
Word Origin and History for umbral
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.
- 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.
- The dark central region of a sunspot. Compare penumbra.