The fully shaded inner region of a shadow cast by an opaque object — the darkest part, where all light is blocked.
From Latin umbra (shadow, shade). The same root gives us umbrella (little shadow), umbrage (offense — originally "shadow of suspicion"), and penumbra (almost shadow). Shadows cast a remarkable vocabulary.
Umbrella means "little shadow." Umbrage means "shadow of suspicion." Penumbra means "almost shadow." One Latin word for darkness generated an entire family of English words, each describing a different quality of shade. Even shadows have shades.
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