Definition of penumbra in US English:

penumbra

nounPlural penumbrae, Plural penumbras

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

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

Origin

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

Pronunciation

penumbra

/pəˈnəmbrə//pəˈnəmbrə/