Definition of penumbra in English:

Share this entry

penumbra

Pronunciation: /pɪˈnʌmbrə/

noun (plural penumbrae /pɪˈnʌmbriː/ or penumbras)

1The partially shaded outer region of the shadow cast by an opaque object.
Example sentences
  • In other cases the Moon does not pass through the umbra at all, just going through the penumbra (a region of partial shadow).
  • And we would do well to remember that the penumbra is the lighter, outer region of the shadow, the halo, indeed, of the shadow.
  • The Moon begins to enter the Earth's outer shadow, or penumbra, at 9: 06 P.M.
1.1 Astronomy The shadow cast by the earth or moon over an area experiencing a partial eclipse.
Example sentences
  • On Friday morning, the moon will enter the penumbra of the Earth's shadow at 3: 05 am, and the moonlight will become dimmer.
  • 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.
  • The Moon on April 24th will glide through Earth's penumbra, producing what astronomers call a ‘penumbral lunar eclipse.’
1.2 Astronomy The less dark outer part of a sunspot, surrounding the core.
Example sentences
  • 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
More example sentences
  • Like many words in everyday use, it carries with it, as it were, a penumbra of different shades of meaning.
  • Others tell different jokes that are incoherent except in the penumbra cast by the joke.
  • 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.

Derivatives

penumbral

Pronunciation: /pɪˈnʌmbrəl/
adjective
Example sentences
  • I think it's important that we recognize the existence of this problematic, penumbral group, but that doesn't mean that there aren't people who do take responsibility.
  • Rick would howl, and then rapidly half-wade, half-swim down the penumbral corridor and stumble up onto the next sandbank, laughing.
  • The nearly flat trail was bordered on one side by precipitous slopes, where penumbral snowfields fell into the crater 100 feet below.

Origin

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

Words that rhyme with penumbra

umbra

For editors and proofreaders

Line breaks: pen|um¦bra

Share this entry
 

What do you find interesting about this word or phrase?

Comments that don't adhere to our Community Guidelines may be moderated or removed.