The umbra, penumbra and antumbra are the names given to three distinct parts of a shadow

Shadow

A shadow is an area where direct light from a light source cannot reach due to obstruction by an object. It occupies all of the space behind an opaque object with light in front of it. The cross section of a shadow is a two-dimensional silhouette, or reverse projection of the object blocking the...

, created by any light source. For a point source only the umbra is cast.

These names are most often used to refer to the shadows cast by celestial bodies

Celestial Body

Celestial Body is a Croatian film directed by Lukas Nola. It was released in 2000....

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The umbra (Latin

Latin

Latin is an Italic language originally spoken in Latium and Ancient Rome. It, along with most European languages, is a descendant of the ancient Proto-Indo-European language. Although it is considered a dead language, a number of scholars and members of the Christian clergy speak it fluently, and...

 for "shadow") is the darkest part of the shadow, where the light source is completely blocked by the occluding body.