penumbra definition

  • noun:
    • A partial shadow, as with an eclipse, between regions of full shadow and full lighting. See Synonyms at color.
    • The grayish outer section of a sunspot.
    • a place in which one thing exists to a smaller or uncertain degree: "1st Amendment has a penumbra in which privacy is protected from governmental intrusion” ( Joseph A. Califano, Jr.)
    • An outlying surrounding region; a periphery: "Downtown Chicago as well as its penumbra additionally stand rejuvenated” ( John McCormick).
    • A partially shaded area around the sides of a shadow, particularly an eclipse.
    • a spot all over edge of a sunspot, darker than the sun's area but lighter as compared to center of sunspot.
    • An area of uncertainly or intermediacy between two mutually unique states or categories.
    • An area that lies in the side of something; a fringe.
    • anything regarding, attached to, and implied by, the existence of another thing that is essential for the next thing becoming full and total in its essential aspects.
    • (in "ischaemic penumbra", after a stroke) a spot associated with mind that has lost only some of its blood circulation, and retains structural integrity but has actually lost function.
    • An incomplete or partial shadow.
    • The shadow cast, in an eclipse, in which the light is partly, however completely, cut-off because of the intervening human body; the room of partial illumination amongst the umbra, or perfect shadow, on all sides, in addition to complete light.
    • The part of a photo where the color imperceptibly blends aided by the light.
    • The limited shadow involving the full light and complete shadow due to an opaque human body intercepting an integral part of the light from a luminous body.
    • The gray fringing edge which encompasses the dark umbra or nucleus of a sun-spot.
    • In painting, the boundary of tone and light, in which the one blends because of the other, the gradation becoming almost imperceptible.
    • A surrounding edge or edge, as in the distribution of metamorphic effects created by an igneous mass.
    • a fringe area of partial shadow around an umbra

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