A vocabulary of landscape — a landscape of words
1469 entries
penumbra
The penumbra is the partial shadow around the edge of a full one, the region where the light source is only partly blocked. In an eclipse, it is the zone from which the sun appears partly covered rather than entirely; on a sunspot it is the lighter fringe around the dark core; and on any shadow cast by an object in ordinary daylight it is the soft border between shade and light.
Etymology
The word is Latin, built from the words for almost and shadow, so it means, precisely, almost-shadow. It was coined by Johannes Kepler in 1604 in a work on optics and astronomy, along with a good deal of the rest of the technical vocabulary of shadows, and it is one of the more durable inventions in the language of science.