UMBRA
Umbra
The umbra, penumbra and antumbra are three distinct parts of a shadow, created by any light source after impinging on an opaque object. For a point source only the umbra is cast.The above text is a snippet from Wikipedia: Umbra
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umbra
Noun
The above text is a snippet from Wiktionary: umbra
and as such is available under the Creative Commons Attribution/Share-Alike License.