• WordNet 3.6
    • n penumbra a fringe region of partial shadow around an umbra
    • ***
Webster's Revised Unabridged Dictionary
    • Penumbra An incomplete or partial shadow.
    • Penumbra (Paint) The part of a picture where the shade imperceptibly blends with the light.
    • Penumbra (Astron) The shadow cast, in an eclipse, where the light is partly, but not wholly, cut off by the intervening body; the space of partial illumination between the umbra, or perfect shadow, on all sides, and the full light.
    • ***
Century Dictionary and Cyclopedia
    • n penumbra The partial shadow between the full light and the total shadow caused by an opaque body intercepting a part of the light from a luminous body. All points within the penumbra are excluded from the view of some part of the luminous body, and are thus partially shaded; while all points within the umbra, or total shadow, are completely excluded from view of the luminous body. The figures represent the so called Hipparchan diagrams of a lunar and a solar eclipse. Any portion of the moon in penumbra appears slightly dimmed, the more so the nearer it is to the umbra. At a station of the earth in the moon's penumbra, the disk of the sun is partially hidden, forming a partial (or, possibly, an annular) eclipse.
    • n penumbra The gray fringing border which surrounds the dark umbra or nucleus of a sun-spot.
    • n penumbra In painting, the boundary of shade and light, where the one blends with the other, the gradation being almost imperceptible.
    • n penumbra A surrounding fringe or border, as in the distribution of metamorphic effects produced by an igneous mass.
    • ***
Chambers's Twentieth Century Dictionary
    • n Penumbra pē-num′bra a partial or lighter shadow round the perfect or darker shadow of an eclipse: the part of a picture where the light and shade blend into each other
    • ***


Webster's Revised Unabridged Dictionary
NL., fr. L. paene, almost + umbra, shade
Chambers's Twentieth Century Dictionary
L. pæne, almost, umbra, shade.


In literature:

The indiscreet touch of a glance brutalizes this vague penumbra.
"Les Misérables Complete in Five Volumes" by Victor Hugo
But as the three stood there a soft whistle sounded from the bushes across the gully, and Jim Burdon pushed a ghostly face into the penumbra.
"Two Sides of the Face" by Arthur Thomas Quiller-Couch
It formed, as it were, a penumbra of fine shrilling, and could be heard for many streets in advance.
"The Dragon Painter" by Mary McNeil Fenollosa
He has touched even the dark penumbra of treason; that could not but risk the sum of his other strivings.
"The Posthumous Works of Thomas De Quincey, Vol. 1 (2 vols)" by Thomas De Quincey
This is the entrance into the "penumbra" (or "Partial shade").
"The Story of Eclipses" by George Chambers
As the Confederate lines advanced, men dropping out of the ranks filled the woods with a penumbra of stragglers.
"From Fort Henry to Corinth" by Manning Ferguson Force
The penumbra will last quite a long time yet, but it will gradually get fainter and fainter.
"Pharaoh's Broker" by Ellsworth Douglass
The idea of change is there, I am willing to grant, but it is hidden in the penumbra.
"Creative Evolution" by Henri Bergson
Within the Penumbra, the Moon is visible; in the Shadow it is nearly invisible.
"The Story of the Heavens" by Robert Stawell Ball
It had a well-marked grayish boundary, and reminded him, though indefinitely fainter, of the penumbra of a sun-spot.
"A Popular History of Astronomy During the Nineteenth Century" by Agnes M. (Agnes Mary) Clerke

In poetry:

His wild penumbra dimly seen
Through shattered glooms and scuds of sleety sheen,
Bold from yonder Norland height
Winter blows his windy horn.
"Song The Eleventh" by Thomas Aird
For stone gathers seed and clouds,
skeleton larks and wolves of penumbra:
but yields not sounds nor crystals nor fire,
only bull rings and bull rings and more bull rings without walls.
"Lament For Ignacio Sanchez Mejias" by Federico Garcia Lorca
Oh, not for aye should agonizing lips
Quiver with questionings they dare not frame;
Though in the dark penumbra of despair
Seemeth no light, nor comfort anywhere--
All things enshadowed as in dense eclipse,
No more the same.
"The Student Gone" by Hattie Howard
I dare not despair nor despond,
Though I grope in the dark for the dawn:
Birth and laughter, and bubbles of breath,
And tears, and the blank void of death,
Round each its penumbra is drawn,--
I touch them,--I see not beyond.
"Questionings" by Kate Seymour Maclean

In news:

Thriller Rod Lott Penumbra is Spanish for "partly in the shadows," which is how we first find the fourth-floor apartment that Margarita Sanchez (Cristina Brondo, Dario Argento's Do You Like Hitchcock.
A solar eclipse showing the moon's shadow on Earth, including the penumbra (large gray oval) and the umbra (black dot).
Wed, Feb 2 : MinneCulture presents a documentary about Penumbra Theatre.
On Monday evening I walked into Penumbra Theatre, having never read a work by James Baldwin .
Penumbra 's 24-hour Bookstore' is a delightful first novel.
In the midst of a financial crisis, the Penumbra Theater in St Paul is suspending plays and laying off staff to survive.
What didn't make the release was the news that Penumbra has selected a successor to Artistic Director Lou Bellamy.
I spoke with Penumbra Managing Director Chris Widdess this afternoon about the cuts.
Penumbra 's 24-Hour Bookstore.
European Launch Of Penumbra Separator 3D Announced At The Working Group In Interventional Neuroradiology (WIN) Seminar.
Penumbra Theater's Julie McGarvie says when she first got the call she had her doubts.
First Penumbra Theatre dropped its annual holiday show "Black Nativity" in order to bring back "I Wish You Love" for a limited run.
Wed, Feb 2: MinneCulture presents a documentary about Penumbra Theatre.
Penumbra 's show Julius By Design, originally scheduled for this season, has been moved to next season in an attempt to keep the books balanced.
Penumbra Theatre featured on MinneCulture.

In science:

By using an input radiation field at two angles, both umbra and penumbra are formed.
A Godunov Method for Multidimensional Radiation Magnetohydrodynamics based on a variable Eddington tensor
This makes the test more difficult, because ad-hoc closures that capture only one direction for the flux will not represent both the umbra and penumbra correctly.
A Godunov Method for Multidimensional Radiation Magnetohydrodynamics based on a variable Eddington tensor
Umbra and penumbra are clearly formed behind the clump.
A Godunov Method for Multidimensional Radiation Magnetohydrodynamics based on a variable Eddington tensor
As Figures 8 and 9 show, the transverse penumbra of a double scattered beam depends on the angular confusion at the patient collimator, θC , which is proportional to ǫ (Eq. 43).
Techniques of Proton Radiotherapy: Transport Theory
Therefore the penumbra can be reduced by placing the second scatterer further upstream, where the beam is smaller. (That is also obvious geometrically from Figure 8.) If the incident beam is small, the first scatterer (no matter how strong) will cause relatively little emittance increase.
Techniques of Proton Radiotherapy: Transport Theory