a region of complete shadow, which is usually applied to eclipses. The area of half or partial
shadow is termed the penumbra.Taken from Dictionary of Science
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The umbra, penumbra and antumbra are the names given to three distinct parts of a shadow, created by any light source. For a point source only the umbra is cast.
These names are usually used when referring to the shadows cast by celestial bodies.
The umbra (Latin for "shadow") is the darkest part of the shadow. From within the umbra, the light source is completely occluded. In astronomy, an observer in the umbra is said to be in the shadows experiencing total eclipse.
Taken from Wikipedia
