penumbra

penumbra is a   Noun

Definition:

[1] An incomplete or partial shadow.

[2] The shadow cast, in an eclipse, where the light is partly, but not wholly, cut off by the intervening body; the space of partial illumination between the umbra, or perfect shadow, on all sides, and the full light. Sir I. Newton.

[3] The part of a picture where the shade imperceptibly blends with the light.

Synonyms: