I. pə̇ˈnəmbrə noun
( plural penumbrae -mˌbrē, -rī ; or penumbras )
Etymology: New Latin, from Latin pene- + umbra shadow — more at umbrage
1. : a shadow cast (as in an eclipse) where the light is partly but not wholly cut off by the intervening body : a space of partial illumination between the perfect shadow on all sides and the full light
2. : the shaded region surrounding the dark central portion of a sunspot
3.
a. : a surrounding or adjoining region in which something exists in a lesser degree : a marginal area : fringe
the penumbra of consciousness
Thracian existed in a sort of cultural penumbra on the border line of the civilized world — Jaan Puhvel
the seventeenth century lay in the penumbra of the middle ages — Edward Eggleston
the few sure findings remain surrounded by a much larger penumbra of uncertainties — A.L.Kroeber
b. : a surrounding atmosphere (as of obscurity, emotion, meaning) : aura , nimbus
love … has been stripped of its mystical penumbra — J.W.Krutch
symbols carrying with them vital penumbras of meaning — M.R.Cohen
c. : an area containing things of obscure classification : an uncertain middle ground between fields of thought or activity : borderland , no-man's-land
orthodoxy and heterodoxy have too large a penumbra of doubt — New Republic
4. : a part of a picture where shade gradually blends with light
• pe·num·bral -rəl adjective
II. noun
: a body of rights held to be guaranteed by implication in a civil constitution
the penumbras of the Bill of Rights