penumbra means A partially shaded area around the edges of a shadow, especially an eclipse. Lexicurio rates it Workaday — a strength score of 10 out of 100.
penumbra is pronounced /pəˈnʌm.bɹə/.
Why “penumbra” is a great word
PENUMBRA — [Noun] A partially shaded region around the edge of a full shadow, especially that cast during an eclipse, or more generally, an area of ambiguity between two distinct states. From New Latin penumbra, from Latin paene ("almost") + umbra ("shadow"). Unlike umbra, which denotes the stark, total darkness at a shadow's heart, or twilight, which is a general atmospheric diffusion, the penumbra is the specific, graded fringe where illumination is neither fully present nor fully absent. It is the dusky fringe of an oak's shade where checkerboards of sun still tremble on the grass, the ghostly, half-lit zone of a lunar eclipse, and the uncertain moral terrain where a clear principle begins to fray. It is the world's most honest territory, the realm where all meaningful transitions must necessarily occur.
noun
- A partially shaded area around the edges of a shadow, especially an eclipse.“[A]ny penumbral fringe that may be detected cannot be well distinguished from the effects of the true penumbræ; […]”
- A region around the edge of a sunspot, darker than the sun's surface but lighter than the middle of the sunspot.“The atmosphere was very clear, evidenced by the steadiness with which the mottling of the sun’s surface and the penumbræ of several spots were visible.”
- An area of uncertainty or intermediacy between two mutually exclusive states or categories.“These firms or businesses are not illegal in the strict sense, but there is a shadowy penumbra within which they live, and it is often convenient for the government to look the other way.”
- An area that lies on the edge of something; a fringe.“Thank God we are not all cowards, we have not all a low ambition, which would make men shades, pœnumbræ^([sic]) of their fellows.”
- 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.“The foregoing [United States Supreme Court] cases suggest that specific guarantees in the Bill of Rights have penumbras, formed by emanations from those guarantees that help give them life and substance.”
- A region of the brain that has lost only some of its blood supply, and retains structural integrity but has lost function.