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the part of a shadow in which there is no light from any light source.
a sharp appearance to the edges of a structure on a radiograph.


radiology An image with sharply defined margins.


(ŭm′bră) [L., shade, shadow]
The edge of the radiographic image proper.


1. Region of very low illumination on a dark background.
2. Zone in which the brightness varies from some illumination to zero (umbra) in the shadow cast by an opaque object intercepting light from an extensive light source. See shadow.
References in periodicals archive ?
The Umbra fine is the result of a license agreement with the well-known Canadian designer of home furnishings.
That is unlikely to change as it enters its fourth decade, but a certain amount of discipline is slowly but surety entering the Umbra lexicon, reflected in assortments that are getting more rounded out with holes in the line being filled in.
At approximately 6:23 am (IST), the umbra of the eclipse will touch the earth at sunrise at a point in the Gulf of Khambhat in the Arabian Sea near the southern coast of Gujarat.
The innovative poetics of the Umbra group drew upon their extensive knowledge of the Anglo-American canon they had been taught in school--something that Dent, among others, felt resentful about--as well as their independent exploration of earlier black writers and their understanding of the African American culture in which, regardless of social class affiliation, they had all been raised.
26 magnitudes dimmer between the time it entered the umbra completely (U2) and mid-eclipse (midway between U2 and U3).
Here the last rays of light to escape from behind the moon refract to form bright beads of light along the whole circumference of the solar umbra.
Umbra predators were dipnetted and seined from Crane Pond and Anax predators were dipnetted from a set of experimental ponds.
umbra (or figura): the sacraments of the Old Testament, which only foreshadowed things to come, signifying but not conferring grace;
Surgamus: solet esse grauis cantantibus umbra, iuniperi grauis umbra; nocent et frugibus umbrae.
The other collection, Umbra vitae (1912), contains posthumous poems, which are modern "night thoughts.