Definition of penumbra in English:


nounPlural penumbrae, Plural penumbras

  • 1The partially shaded outer region of the shadow cast by an opaque object.

    • ‘Shadows and penumbras were instantaneously formed from the myriad of trees and hills that he surveyed through the window, and just as quickly vanished.’
    • ‘He is pacing up and down the library in the gloom, ‘the penumbra of the library’, as he put it, and he thinks of a tiger in the jungle, and this is ‘The Other Tiger’.’
    • ‘He brings a sharp eye to the bedside of a poet friend and to urban decay, ‘the dust of voices, / the smoky penumbra around streetlights.’’
    • ‘Our planet's shadow has two parts, a dark inner core called the umbra and a pale outer fringe called the penumbra.’
    • ‘He stands within the penumbra of the falls, near the top of Irish Mountain.’
    • ‘The black penumbra which appears when you first look to its edges soon becomes brown.’
    • ‘The penumbra of his face, and the emanations of light leaking from behind his ears, and his hair, was blinding.’
    • ‘Neon glow qualifies the relation of work to wall; each piece generates its own set of shadow and penumbra.’
    • ‘And we would do well to remember that the penumbra is the lighter, outer region of the shadow, the halo, indeed, of the shadow.’
    • ‘In other cases the Moon does not pass through the umbra at all, just going through the penumbra (a region of partial shadow).’
    • ‘A penumbra of fiery purple encircles this near-seamless construction of photographs, objects and painted images on wood.’
    • ‘The Moon begins to enter the Earth's outer shadow, or penumbra, at 9: 06 P.M.’
    • ‘Long, thin filaments radiate from the umbra into a brighter surrounding region called the penumbra.’
    1. 1.1Astronomy The shadow cast by the earth or moon over an area experiencing a partial eclipse.
      • ‘A penumbral eclipse, sometimes called an appulse, occurs when the Moon misses the Earth's umbra but passes through its penumbra or secondary shadow.’
      • ‘The Moon on April 24th will glide through Earth's penumbra, producing what astronomers call a ‘penumbral lunar eclipse.’’
      • ‘So, one will observe either a total eclipse by the umbra (which can be well observed), a partial eclipse by the umbra and penumbra, or a total or partial eclipse by the penumbra only.’
      • ‘On Friday morning, the moon will enter the penumbra of the Earth's shadow at 3: 05 am, and the moonlight will become dimmer.’
      • ‘As the partial phase progresses, you are moving deeper and deeper into the Moon's penumbra.’
      silhouette, outline, shape, contour, profile
      View synonyms
    2. 1.2Astronomy The less dark outer part of a sunspot, surrounding the core.
      • ‘Theorists suspect that the penumbra is key to keeping a sunspot intact.’
  • 2A peripheral or indeterminate area or group.

    ‘an immense penumbra of theory surrounds any observation’
    • ‘My guess is that eliminating the double taxation of dividends would lead to a powerful rally in stock prices and would do much to lift the penumbra of uncertainty that has bedeviled both consumers and corporate managers.’
    • ‘He had a sound belief in astrology, the stars being the twinkling penumbra of his incandescent belief in the ‘free market,’ with whose motions it was blasphemous to tamper.’
    • ‘Others tell different jokes that are incoherent except in the penumbra cast by the joke.’
    • ‘Like many words in everyday use, it carries with it, as it were, a penumbra of different shades of meaning.’
    • ‘If the court could remove the legal impediments to education provided by the state, why couldn't it also read, in penumbras and emanations, any number of other rights and privileges that they thought it would be nice for people to have?’


Mid 17th century: modern Latin, from Latin paene ‘almost’ + umbra ‘shadow’.