First Known Use: 1665
Dictionary
penumbra
noun pen·um·bra \pə-ˈnəm-brə\
plural pen·um·brae\-(ˌ)brē, -ˌbrī\ or pen·um·bras
Definition of PENUMBRA
1
a : a space of partial illumination (as in an eclipse) between the perfect shadow on all sides and the full light b : a shaded region surrounding the dark central portion of a sunspot
2
: a surrounding or adjoining region in which something exists in a lesser degree : fringe
3
: a body of rights held to be guaranteed by implication in a civil constitution
4
: something that covers, surrounds, or obscures : shroud <a penumbra of secrecy> <a penumbra of somber dignity has descended over his reputation — James Atlas>
— pen·um·bral \-brəl\ adjective
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Origin of PENUMBRA
New Latin, from Latin paene almost + umbra shadow — more at umbrage
Medical Dictionary
penumbra
noun pe·num·bra \pə-ˈnəm-brə\
plural pe·num·brae \-(ˌ)brē, -ˌbrī\ or pe·num·bras
Medical Definition of PENUMBRA
: a blurred area in a radiograph at the edge of an anatomical structure
—pe·num·bral \-brəl\ adjective
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