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penumbra

Syllabification: pe·num·bra
Pronunciation: /pəˈnəmbrə
 
/

Definition of penumbra in English:

noun (plural penumbrae /-brē, -brī/ 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 dark core.
Example sentences
  • Theorists suspect that the penumbra is key to keeping a sunspot intact.

Origin

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

Derivatives

penumbral

1
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.

Words that rhyme with penumbra

umbra

Definition of penumbra in:

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