(pĭ-nŭm'brə) Pluralpenumbras or penumbrae (pĭ-nŭm'brē)
A partial shadow between regions of full shadow (the umbra) and full illumination, especially as cast by Earth, the Moon, or another body during an eclipse. During a partial lunar eclipse, a portion of the Moon's disk remains within the penumbra of Earth's shadow while the rest is darkened by the umbra. See Note at eclipse.
The grayish outer part of a sunspot. Compare umbra.