penumbra

• 名词，指半影，即天体阴影中较暗本影周围较亮的边缘区域；也泛指任何处于边缘或过渡状态的部分。

A noun referring to a fringe region of partial shadow that surrounds the darkest part of a shadow (the umbra), often used in astronomy or optics.

1. Partial shadowC1formalscientific

   The outer, lighter part of a shadow, especially in an eclipse, where the light source is only partially blocked.

   半影

   • During a partial solar eclipse, the moon's penumbra falls on Earth.
   • The penumbra of the shadow was barely visible on the ground.
   • Astronomers study the penumbra to understand the geometry of eclipses.

2. Fringe or borderline areaC2formal

   A peripheral or ambiguous region that is not fully defined or illuminated, often used metaphorically.

   边缘地带

   • The issue lies in the penumbra of the law, where interpretation is required.
   • His argument existed in the penumbra between fact and fiction.
   • The penumbra of uncertainty surrounded the decision.

   同义词borderlandborderlineedgefringegray areamarginperipherytwilight zone