penumbra.

1. A region of partial shadow where some, but not all, of a light source is obscured.

2. An indistinct fringe surrounding a clear idea, event, or area of influence.

Use it for

Words that belong together

• lunar penumbra
• edge of the penumbra
• penumbra of a shadow

On the page

The wall lay in the lamp’s penumbra.

The moon entered the Earth’s penumbra.

A soft penumbra surrounded the sharply defined shadow.

Usage notes

Primary category: gothic. Forms: Singular penumbra; plural penumbras or penumbrae. Legacy lexical fields mirror sense 1 only. Use numbered sense fields for all meanings.