Penumbra is a noun that means almost darkness. It can be defined as a transition point that exists between light and dark and for this reason it has the sense of almost dark.
Penumbra occurs between light and darkness, when there is a partial blockage between the light source and the illuminated object. A popular expression for the penumbra is half light.
The word comes from the Latin terms pains (almost) and umbra (full shade).
Can be synonyms of penumbra: mist, half light, twilight, gloomy and haze. Can be antonyms: darkness, darkness, obscured.
Relationships and differences between shadow and penumbra
There is a relationship between the words penumbra and shadow. In Astronomy, penumbra is defined as an area of shadow that exists between lighted spaces and completely dark spaces during an eclipse.
However, according to physics, there are differences between shadow and twilight.
Shadow is a region that is not reached by light, when there is an opaque obstacle in front of a source of light rays. The penumbra is an area around the shadow, where there are some bright spots. It is the almost dark area that lies between light and shadow.
See the meanings of Eclipse and Solar eclipse.
Difference between Penumbra and Umbra
Also according to Physics, for penumbra to exist, the light source must be extensive, as is the case with sunlight. If it is not extensive, such as artificial lighting, the light source is called spot and the shaded area is called umbra.
The word penumbra also appears in Medicine. The ischemic penumbra is an area that surrounds the brain region where an ischemic stroke (stroke) occurs.
See more about the meaning of stroke.
