1. the partially shaded outer regions of the shadow cast by an opaque object
Usage: astronomy; physics
2. a surrounding area or fringe where something exists to a lesser or uncertain degree
Usage: figurative

Examples

• During the eclipse, observers in the penumbras experienced only a partial darkening of the sun.
• The moon’s penumbras created a gradient of shadow across the Earth’s surface.
• The policy exists in the penumbras of constitutional law.
• Artists often work in the penumbras between different creative disciplines.
• The penumbras of the forest provided dappled light for the hiking trail.
• Legal scholars debate the penumbras of privacy rights.
• The penumbras of the building cast interesting patterns on the sidewalk.