Full moon - penumbral lunar eclipse
An example of the penumbra is the outer lighted area surrounding the shadow of the moon which is created during an eclipse.
nounpl. -·brae· or -·bras
- the partly lighted area surrounding the complete shadow (umbra) of a body, as the moon, during an eclipse
- the less dark region surrounding the dark central area of a sunspot
- a vague, indefinite, or borderline area
Origin of penumbraModern Latin from paene, almost (see passion) + umbra, shade
nounpl. pe·num·bras, or pe·num·brae
- A partial shadow, as in an eclipse, between regions of complete shadow and complete illumination.
- The diffuse outer part of a sunspot.
- An area in which something exists to a lesser or uncertain degree: “The First Amendment has a penumbra where privacy is protected from governmental intrusion” ( Joseph A. Califano, Jr. )
- An outlying surrounding region; a periphery: “Downtown Chicago and its penumbra also stand rejuvenated” ( John McCormick )
Origin of penumbraNew Latin pēnumbra Latin paene almost Latin umbra shadow
- pe·num′bral pe·num′brous
- A partially shaded area around the edges of a shadow, especially an eclipse.
- (astronomy) A region around the edge of a sunspot, darker than the sun's surface but lighter than the middle of the sunspot.
- (figuratively) An area of uncertainly or intermediacy between two mutually exclusive states or categories.
- (figuratively) An area that lies on the edge of something; a fringe.
- Something related to, connected to, and implied by, the existence of something else that is necessary for the second thing to be full and complete in its essential aspects.
- (medicine) (in "ischaemic penumbra", after a stroke) A region of the brain that has lost only some of its blood supply, and retains structural integrity but has lost function.