means The umbra is the fully dark central region of a shadow, where the source of light is completely blocked, as in the deepest part of a solar eclipse's shadow.

from Straight from the Latin umbra, meaning "shadow" or "shade" — the same word the Romans used for everything from a tree's cool patch to a ghost lingering in the underworld. It casts a long shadow across English: umbrella (a "little shade" from the sun, via Italian ombrella), umbrage (originally just shade, later the shadowy feeling of being offended), and adumbrate (to sketch in shadowy outline). The penumbra, that softer fringe of partial shadow, is literally the "almost-shadow," from paene ("almost") plus umbra.