Umbra

:A different sense of the word "umbra", used in mathematics, is explained in the article titled umbral calculus.

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The umbra (Latin for shadow) is the darkest part of a shadow. From within the umbra, the source of light is completely blocked by the object causing the shadow. This contrasts with the penumbra where the light source is only partially blocked and there is only a partial shadow.

Related Topics:
Latin - Shadow - Light - Penumbra

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The umbra is also the comparatively dark central region of a sunspot.

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