The word penumbra is derived from the Latin word paene which means almost and umbra which means shadow. Penumbra is that section in which light source is hidden or covered by the occluding body. This usually happens with celestial objects. A person or an observer that is present in the penumbra region will experience a partial eclipse. Penumbra is that region that lies between the umbra and antumbra. It means it lies between an area of complete illumination and complete darkness. Penumbra usually refers to shadows of celestial or opaque objects that falls on a particular region.